diff --git a/InvenTree/InvenTree/serializers.py b/InvenTree/InvenTree/serializers.py
index 1d0e70908d..89ea434d0c 100644
--- a/InvenTree/InvenTree/serializers.py
+++ b/InvenTree/InvenTree/serializers.py
@@ -583,4 +583,4 @@ class DataFileExtractSerializer(serializers.Serializer):
 
     def save(self):
         """No "save" action for this serializer."""
-        ...
+        pass
diff --git a/InvenTree/part/__init__.py b/InvenTree/part/__init__.py
index 1416c9a025..1412ff8f11 100644
--- a/InvenTree/part/__init__.py
+++ b/InvenTree/part/__init__.py
@@ -1,8 +1 @@
-"""The Part module is responsible for Part management.
-
-It includes models for:
-
-- PartCategory
-- Part
-- BomItem
-"""
+"""The Part module is responsible for Part management."""
diff --git a/InvenTree/part/admin.py b/InvenTree/part/admin.py
index 81e408b30d..9c1648e616 100644
--- a/InvenTree/part/admin.py
+++ b/InvenTree/part/admin.py
@@ -1,3 +1,5 @@
+"""Admin class definitions for the 'part' app"""
+
 from django.contrib import admin
 
 import import_export.widgets as widgets
@@ -38,6 +40,7 @@ class PartResource(ModelResource):
     building = Field(attribute='quantity_being_built', readonly=True, widget=widgets.IntegerWidget())
 
     class Meta:
+        """Metaclass definition"""
         model = models.Part
         skip_unchanged = True
         report_skipped = False
@@ -61,8 +64,17 @@ class PartResource(ModelResource):
 
         return query
 
+    def after_import(self, dataset, result, using_transactions, dry_run, **kwargs):
+        """Rebuild MPTT tree structure after importing Part data"""
+
+        super().after_import(dataset, result, using_transactions, dry_run, **kwargs)
+
+        # Rebuild the Part tree(s)
+        models.Part.objects.rebuild()
+
 
 class PartAdmin(ImportExportModelAdmin):
+    """Admin class for the Part model"""
 
     resource_class = PartResource
 
@@ -90,6 +102,7 @@ class PartCategoryResource(ModelResource):
     default_location = Field(attribute='default_location', widget=widgets.ForeignKeyWidget(StockLocation))
 
     class Meta:
+        """Metaclass definition"""
         model = models.PartCategory
         skip_unchanged = True
         report_skipped = False
@@ -102,6 +115,7 @@ class PartCategoryResource(ModelResource):
         ]
 
     def after_import(self, dataset, result, using_transactions, dry_run, **kwargs):
+        """Rebuild MPTT tree structure after importing PartCategory data"""
 
         super().after_import(dataset, result, using_transactions, dry_run, **kwargs)
 
@@ -110,6 +124,7 @@ class PartCategoryResource(ModelResource):
 
 
 class PartCategoryAdmin(ImportExportModelAdmin):
+    """Admin class for the PartCategory model"""
 
     resource_class = PartCategoryResource
 
@@ -127,27 +142,15 @@ class PartRelatedAdmin(admin.ModelAdmin):
 
 
 class PartAttachmentAdmin(admin.ModelAdmin):
+    """Admin class for the PartAttachment model"""
 
     list_display = ('part', 'attachment', 'comment')
 
     autocomplete_fields = ('part',)
 
 
-class PartStarAdmin(admin.ModelAdmin):
-
-    list_display = ('part', 'user')
-
-    autocomplete_fields = ('part',)
-
-
-class PartCategoryStarAdmin(admin.ModelAdmin):
-
-    list_display = ('category', 'user')
-
-    autocomplete_fields = ('category',)
-
-
 class PartTestTemplateAdmin(admin.ModelAdmin):
+    """Admin class for the PartTestTemplate model"""
 
     list_display = ('part', 'test_name', 'required')
 
@@ -193,7 +196,7 @@ class BomItemResource(ModelResource):
         return float(item.quantity)
 
     def before_export(self, queryset, *args, **kwargs):
-
+        """Perform before exporting data"""
         self.is_importing = kwargs.get('importing', False)
 
     def get_fields(self, **kwargs):
@@ -229,6 +232,7 @@ class BomItemResource(ModelResource):
         return fields
 
     class Meta:
+        """Metaclass definition"""
         model = models.BomItem
         skip_unchanged = True
         report_skipped = False
@@ -243,6 +247,7 @@ class BomItemResource(ModelResource):
 
 
 class BomItemAdmin(ImportExportModelAdmin):
+    """Admin class for the BomItem model"""
 
     resource_class = BomItemResource
 
@@ -254,6 +259,8 @@ class BomItemAdmin(ImportExportModelAdmin):
 
 
 class ParameterTemplateAdmin(ImportExportModelAdmin):
+    """Admin class for the PartParameterTemplate model"""
+
     list_display = ('name', 'units')
 
     search_fields = ('name', 'units')
@@ -271,6 +278,7 @@ class ParameterResource(ModelResource):
     template_name = Field(attribute='template__name', readonly=True)
 
     class Meta:
+        """Metaclass definition"""
         model = models.PartParameter
         skip_unchanged = True
         report_skipped = False
@@ -278,6 +286,7 @@ class ParameterResource(ModelResource):
 
 
 class ParameterAdmin(ImportExportModelAdmin):
+    """Admin class for the PartParameter model"""
 
     resource_class = ParameterResource
 
@@ -287,21 +296,26 @@ class ParameterAdmin(ImportExportModelAdmin):
 
 
 class PartCategoryParameterAdmin(admin.ModelAdmin):
+    """Admin class for the PartCategoryParameterTemplate model"""
 
     autocomplete_fields = ('category', 'parameter_template',)
 
 
 class PartSellPriceBreakAdmin(admin.ModelAdmin):
+    """Admin class for the PartSellPriceBreak model"""
 
     class Meta:
+        """Metaclass definition"""
         model = models.PartSellPriceBreak
 
     list_display = ('part', 'quantity', 'price',)
 
 
 class PartInternalPriceBreakAdmin(admin.ModelAdmin):
+    """Admin class for the PartInternalPriceBreak model"""
 
     class Meta:
+        """Metaclass definition"""
         model = models.PartInternalPriceBreak
 
     list_display = ('part', 'quantity', 'price',)
@@ -313,8 +327,6 @@ admin.site.register(models.Part, PartAdmin)
 admin.site.register(models.PartCategory, PartCategoryAdmin)
 admin.site.register(models.PartRelated, PartRelatedAdmin)
 admin.site.register(models.PartAttachment, PartAttachmentAdmin)
-admin.site.register(models.PartStar, PartStarAdmin)
-admin.site.register(models.PartCategoryStar, PartCategoryStarAdmin)
 admin.site.register(models.BomItem, BomItemAdmin)
 admin.site.register(models.PartParameterTemplate, ParameterTemplateAdmin)
 admin.site.register(models.PartParameter, ParameterAdmin)
diff --git a/InvenTree/part/api.py b/InvenTree/part/api.py
index 569a0491f2..8004cf1326 100644
--- a/InvenTree/part/api.py
+++ b/InvenTree/part/api.py
@@ -49,7 +49,7 @@ class CategoryList(generics.ListCreateAPIView):
     serializer_class = part_serializers.CategorySerializer
 
     def get_serializer_context(self):
-
+        """Add extra context data to the serializer for the PartCategoryList endpoint"""
         ctx = super().get_serializer_context()
 
         try:
@@ -161,7 +161,7 @@ class CategoryDetail(generics.RetrieveUpdateDestroyAPIView):
     queryset = PartCategory.objects.all()
 
     def get_serializer_context(self):
-
+        """Add extra context to the serializer for the CategoryDetail endpoint"""
         ctx = super().get_serializer_context()
 
         try:
@@ -173,7 +173,7 @@ class CategoryDetail(generics.RetrieveUpdateDestroyAPIView):
         return ctx
 
     def update(self, request, *args, **kwargs):
-
+        """Perform 'update' function and mark this part as 'starred' (or not)"""
         if 'starred' in request.data:
             starred = str2bool(request.data.get('starred', False))
 
@@ -188,6 +188,7 @@ class CategoryMetadata(generics.RetrieveUpdateAPIView):
     """API endpoint for viewing / updating PartCategory metadata."""
 
     def get_serializer(self, *args, **kwargs):
+        """Return a MetadataSerializer pointing to the referenced PartCategory instance"""
         return MetadataSerializer(PartCategory, *args, **kwargs)
 
     queryset = PartCategory.objects.all()
@@ -370,7 +371,7 @@ class PartThumbs(generics.ListAPIView):
     serializer_class = part_serializers.PartThumbSerializer
 
     def get_queryset(self):
-
+        """Return a queryset which exlcudes any parts without images"""
         queryset = super().get_queryset()
 
         # Get all Parts which have an associated image
@@ -432,7 +433,7 @@ class PartScheduling(generics.RetrieveAPIView):
     queryset = Part.objects.all()
 
     def retrieve(self, request, *args, **kwargs):
-
+        """Return scheduling information for the referenced Part instance"""
         today = datetime.datetime.now().date()
 
         part = self.get_object()
@@ -555,6 +556,7 @@ class PartMetadata(generics.RetrieveUpdateAPIView):
     """API endpoint for viewing / updating Part metadata."""
 
     def get_serializer(self, *args, **kwargs):
+        """Returns a MetadataSerializer instance pointing to the referenced Part"""
         return MetadataSerializer(Part, *args, **kwargs)
 
     queryset = Part.objects.all()
@@ -566,7 +568,7 @@ class PartSerialNumberDetail(generics.RetrieveAPIView):
     queryset = Part.objects.all()
 
     def retrieve(self, request, *args, **kwargs):
-
+        """Return serial number information for the referenced Part instance"""
         part = self.get_object()
 
         # Calculate the "latest" serial number
@@ -592,7 +594,7 @@ class PartCopyBOM(generics.CreateAPIView):
     serializer_class = part_serializers.PartCopyBOMSerializer
 
     def get_serializer_context(self):
-
+        """Add custom information to the serializer context for this endpoint"""
         ctx = super().get_serializer_context()
 
         try:
@@ -607,8 +609,10 @@ class PartValidateBOM(generics.RetrieveUpdateAPIView):
     """API endpoint for 'validating' the BOM for a given Part."""
 
     class BOMValidateSerializer(serializers.ModelSerializer):
+        """Simple serializer class for validating a single BomItem instance"""
 
         class Meta:
+            """Metaclass defines serializer fields"""
             model = Part
             fields = [
                 'checksum',
@@ -628,6 +632,7 @@ class PartValidateBOM(generics.RetrieveUpdateAPIView):
         )
 
         def validate_valid(self, valid):
+            """Check that the 'valid' input was flagged"""
             if not valid:
                 raise ValidationError(_('This option must be selected'))
 
@@ -636,7 +641,7 @@ class PartValidateBOM(generics.RetrieveUpdateAPIView):
     serializer_class = BOMValidateSerializer
 
     def update(self, request, *args, **kwargs):
-
+        """Validate the referenced BomItem instance"""
         part = self.get_object()
 
         partial = kwargs.pop('partial', False)
@@ -660,6 +665,7 @@ class PartDetail(generics.RetrieveUpdateDestroyAPIView):
     starred_parts = None
 
     def get_queryset(self, *args, **kwargs):
+        """Return an annotated queryset object for the PartDetail endpoint"""
         queryset = super().get_queryset(*args, **kwargs)
 
         queryset = part_serializers.PartSerializer.annotate_queryset(queryset)
@@ -667,7 +673,7 @@ class PartDetail(generics.RetrieveUpdateDestroyAPIView):
         return queryset
 
     def get_serializer(self, *args, **kwargs):
-
+        """Return a serializer instance for the PartDetail endpoint"""
         # By default, include 'category_detail' information in the detail view
         try:
             kwargs['category_detail'] = str2bool(self.request.query_params.get('category_detail', True))
@@ -687,7 +693,11 @@ class PartDetail(generics.RetrieveUpdateDestroyAPIView):
         return self.serializer_class(*args, **kwargs)
 
     def destroy(self, request, *args, **kwargs):
-        # Retrieve part
+        """Delete a Part instance via the API
+
+        - If the part is 'active' it cannot be deleted
+        - It must first be marked as 'inactive'
+        """
         part = Part.objects.get(pk=int(kwargs['pk']))
         # Check if inactive
         if not part.active:
@@ -695,7 +705,7 @@ class PartDetail(generics.RetrieveUpdateDestroyAPIView):
             return super(PartDetail, self).destroy(request, *args, **kwargs)
         else:
             # Return 405 error
-            message = f'Part \'{part.name}\' (pk = {part.pk}) is active: cannot delete'
+            message = 'Part is active: cannot delete'
             return Response(status=status.HTTP_405_METHOD_NOT_ALLOWED, data=message)
 
     def update(self, request, *args, **kwargs):
@@ -723,7 +733,7 @@ class PartFilter(rest_filters.FilterSet):
     has_ipn = rest_filters.BooleanFilter(label='Has IPN', method='filter_has_ipn')
 
     def filter_has_ipn(self, queryset, name, value):
-
+        """Filter by whether the Part has an IPN (internal part number) or not"""
         value = str2bool(value)
 
         if value:
@@ -768,7 +778,7 @@ class PartFilter(rest_filters.FilterSet):
     has_stock = rest_filters.BooleanFilter(label='Has stock', method='filter_has_stock')
 
     def filter_has_stock(self, queryset, name, value):
-
+        """Filter by whether the Part has any stock"""
         value = str2bool(value)
 
         if value:
@@ -782,7 +792,7 @@ class PartFilter(rest_filters.FilterSet):
     unallocated_stock = rest_filters.BooleanFilter(label='Unallocated stock', method='filter_unallocated_stock')
 
     def filter_unallocated_stock(self, queryset, name, value):
-
+        """Filter by whether the Part has unallocated stock"""
         value = str2bool(value)
 
         if value:
@@ -837,7 +847,7 @@ class PartList(APIDownloadMixin, generics.ListCreateAPIView):
     starred_parts = None
 
     def get_serializer(self, *args, **kwargs):
-
+        """Return a serializer instance for this endpoint"""
         # Ensure the request context is passed through
         kwargs['context'] = self.get_serializer_context()
 
@@ -859,6 +869,7 @@ class PartList(APIDownloadMixin, generics.ListCreateAPIView):
         return self.serializer_class(*args, **kwargs)
 
     def download_queryset(self, queryset, export_format):
+        """Download the filtered queryset as a data file"""
         dataset = PartResource().export(queryset=queryset)
 
         filedata = dataset.export(export_format)
@@ -1077,17 +1088,14 @@ class PartList(APIDownloadMixin, generics.ListCreateAPIView):
         return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)
 
     def get_queryset(self, *args, **kwargs):
-
+        """Return an annotated queryset object"""
         queryset = super().get_queryset(*args, **kwargs)
         queryset = part_serializers.PartSerializer.annotate_queryset(queryset)
 
         return queryset
 
     def filter_queryset(self, queryset):
-        """Perform custom filtering of the queryset.
-
-        We overide the DRF filter_fields here because
-        """
+        """Perform custom filtering of the queryset"""
         params = self.request.query_params
 
         queryset = super().filter_queryset(queryset)
@@ -1345,7 +1353,7 @@ class PartRelatedList(generics.ListCreateAPIView):
     serializer_class = part_serializers.PartRelationSerializer
 
     def filter_queryset(self, queryset):
-
+        """Custom queryset filtering"""
         queryset = super().filter_queryset(queryset)
 
         params = self.request.query_params
@@ -1478,8 +1486,7 @@ class BomFilter(rest_filters.FilterSet):
     validated = rest_filters.BooleanFilter(label='BOM line has been validated', method='filter_validated')
 
     def filter_validated(self, queryset, name, value):
-
-        # Work out which lines have actually been validated
+        """Filter by which lines have actually been validated"""
         pks = []
 
         value = str2bool(value)
@@ -1512,6 +1519,7 @@ class BomList(generics.ListCreateAPIView):
     filterset_class = BomFilter
 
     def list(self, request, *args, **kwargs):
+        """Return serialized list response for this endpoint"""
 
         queryset = self.filter_queryset(self.get_queryset())
 
@@ -1537,6 +1545,13 @@ class BomList(generics.ListCreateAPIView):
             return Response(data)
 
     def get_serializer(self, *args, **kwargs):
+        """Return the serializer instance for this API endpoint
+
+        If requested, extra detail fields are annotated to the queryset:
+        - part_detail
+        - sub_part_detail
+        - include_pricing
+        """
 
         # Do we wish to include extra detail?
         try:
@@ -1561,7 +1576,7 @@ class BomList(generics.ListCreateAPIView):
         return self.serializer_class(*args, **kwargs)
 
     def get_queryset(self, *args, **kwargs):
-
+        """Return the queryset object for this endpoint"""
         queryset = super().get_queryset(*args, **kwargs)
 
         queryset = self.get_serializer_class().setup_eager_loading(queryset)
@@ -1570,7 +1585,7 @@ class BomList(generics.ListCreateAPIView):
         return queryset
 
     def filter_queryset(self, queryset):
-
+        """Custom query filtering for the BomItem list API"""
         queryset = super().filter_queryset(queryset)
 
         params = self.request.query_params
@@ -1766,7 +1781,7 @@ class BomDetail(generics.RetrieveUpdateDestroyAPIView):
     serializer_class = part_serializers.BomItemSerializer
 
     def get_queryset(self, *args, **kwargs):
-
+        """Prefetch related fields for this queryset"""
         queryset = super().get_queryset(*args, **kwargs)
 
         queryset = self.get_serializer_class().setup_eager_loading(queryset)
@@ -1778,9 +1793,8 @@ class BomDetail(generics.RetrieveUpdateDestroyAPIView):
 class BomItemValidate(generics.UpdateAPIView):
     """API endpoint for validating a BomItem."""
 
-    # Very simple serializers
     class BomItemValidationSerializer(serializers.Serializer):
-
+        """Simple serializer for passing a single boolean field"""
         valid = serializers.BooleanField(default=False)
 
     queryset = BomItem.objects.all()
diff --git a/InvenTree/part/apps.py b/InvenTree/part/apps.py
index dff059d92a..9a8ce076b5 100644
--- a/InvenTree/part/apps.py
+++ b/InvenTree/part/apps.py
@@ -1,3 +1,5 @@
+"""part app specification"""
+
 import logging
 
 from django.apps import AppConfig
@@ -9,6 +11,7 @@ logger = logging.getLogger("inventree")
 
 
 class PartConfig(AppConfig):
+    """Config class for the 'part' app"""
     name = 'part'
 
     def ready(self):
diff --git a/InvenTree/part/forms.py b/InvenTree/part/forms.py
index 965f476e21..f4c4810d37 100644
--- a/InvenTree/part/forms.py
+++ b/InvenTree/part/forms.py
@@ -5,7 +5,6 @@ from django.utils.translation import gettext_lazy as _
 
 from mptt.fields import TreeNodeChoiceField
 
-import common.models
 from common.forms import MatchItemForm
 from InvenTree.fields import RoundingDecimalFormField
 from InvenTree.forms import HelperForm
@@ -16,20 +15,6 @@ from .models import (Part, PartCategory, PartCategoryParameterTemplate,
                      PartSellPriceBreak)
 
 
-class PartModelChoiceField(forms.ModelChoiceField):
-    """Extending string representation of Part instance with available stock."""
-
-    def label_from_instance(self, part):
-
-        label = str(part)
-
-        # Optionally display available part quantity
-        if common.models.InvenTreeSetting.get_setting('PART_SHOW_QUANTITY_IN_FORMS'):
-            label += f" - {part.available_stock}"
-
-        return label
-
-
 class PartImageDownloadForm(HelperForm):
     """Form for downloading an image from a URL."""
 
@@ -40,6 +25,7 @@ class PartImageDownloadForm(HelperForm):
     )
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = Part
         fields = [
             'url',
@@ -78,6 +64,7 @@ class EditPartParameterTemplateForm(HelperForm):
     """Form for editing a PartParameterTemplate object."""
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = PartParameterTemplate
         fields = [
             'name',
@@ -97,6 +84,7 @@ class EditCategoryParameterTemplateForm(HelperForm):
                                                help_text=_('Add parameter template to all categories'))
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = PartCategoryParameterTemplate
         fields = [
             'category',
@@ -118,6 +106,7 @@ class PartPriceForm(forms.Form):
     )
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = Part
         fields = [
             'quantity',
@@ -130,6 +119,7 @@ class EditPartSalePriceBreakForm(HelperForm):
     quantity = RoundingDecimalFormField(max_digits=10, decimal_places=5, label=_('Quantity'))
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = PartSellPriceBreak
         fields = [
             'part',
@@ -144,6 +134,7 @@ class EditPartInternalPriceBreakForm(HelperForm):
     quantity = RoundingDecimalFormField(max_digits=10, decimal_places=5, label=_('Quantity'))
 
     class Meta:
+        """Metaclass defines fields for this form"""
         model = PartInternalPriceBreak
         fields = [
             'part',
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index 8834756b29..29a8f8ec13 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -103,12 +103,15 @@ class PartCategory(MetadataMixin, InvenTreeTree):
 
     @staticmethod
     def get_api_url():
+        """Return the API url associated with the PartCategory model"""
         return reverse('api-part-category-list')
 
     def get_absolute_url(self):
+        """Return the web URL associated with the detail view for this PartCategory instance"""
         return reverse('category-detail', kwargs={'pk': self.id})
 
     class Meta:
+        """Metaclass defines extra model properties"""
         verbose_name = _("Part Category")
         verbose_name_plural = _("Part Categories")
 
@@ -131,6 +134,7 @@ class PartCategory(MetadataMixin, InvenTreeTree):
 
     @property
     def item_count(self):
+        """Return the number of parts contained in this PartCategory"""
         return self.partcount()
 
     def partcount(self, cascade=True, active=False):
@@ -284,7 +288,7 @@ class PartManager(TreeManager):
     """
 
     def get_queryset(self):
-
+        """Perform default prefetch operations when accessing Part model from the database"""
         return super().get_queryset().prefetch_related(
             'category',
             'category__parent',
@@ -333,6 +337,7 @@ class Part(MetadataMixin, MPTTModel):
     objects = PartManager()
 
     class Meta:
+        """Metaclass defines extra model properties"""
         verbose_name = _("Part")
         verbose_name_plural = _("Parts")
         ordering = ['name', ]
@@ -341,12 +346,13 @@ class Part(MetadataMixin, MPTTModel):
         ]
 
     class MPTTMeta:
+        """MPTT metaclass definitions"""
         # For legacy reasons the 'variant_of' field is used to indicate the MPTT parent
         parent_attr = 'variant_of'
 
     @staticmethod
     def get_api_url():
-
+        """Return the list API endpoint URL associated with the Part model"""
         return reverse('api-part-list')
 
     def api_instance_filters(self):
@@ -450,6 +456,7 @@ class Part(MetadataMixin, MPTTModel):
                                 pass
 
     def __str__(self):
+        """Return a string representation of the Part (for use in the admin interface)"""
         return f"{self.full_name} - {self.description}"
 
     def get_parts_in_bom(self, **kwargs):
@@ -665,15 +672,6 @@ class Part(MetadataMixin, MPTTModel):
 
             return ' | '.join(elements)
 
-    def set_category(self, category):
-
-        # Ignore if the category is already the same
-        if self.category == category:
-            return
-
-        self.category = category
-        self.save()
-
     def get_absolute_url(self):
         """Return the web URL for viewing this part."""
         return reverse('part-detail', kwargs={'pk': self.id})
@@ -956,6 +954,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def category_path(self):
+        """Return the category path of this Part instance"""
         if self.category:
             return self.category.pathstring
         return ''
@@ -1442,6 +1441,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def has_bom(self):
+        """Return True if this Part instance has any BOM items"""
         return self.get_bom_items().count() > 0
 
     def get_trackable_parts(self):
@@ -1605,7 +1605,17 @@ class Part(MetadataMixin, MPTTModel):
         return "{a} - {b}".format(a=min_price, b=max_price)
 
     def get_supplier_price_range(self, quantity=1):
+        """Return the supplier price range of this part:
 
+        - Checks if there is any supplier pricing information associated with this Part
+        - Iterate through available supplier pricing and select (min, max)
+        - Returns tuple of (min, max)
+
+        Arguments:
+            quantity: Quantity at which to calculate price (default=1)
+
+        Returns: (min, max) tuple or (None, None) if no supplier pricing available
+        """
         min_price = None
         max_price = None
 
@@ -1719,6 +1729,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def has_price_breaks(self):
+        """Return True if this part has sale price breaks"""
         return self.price_breaks.count() > 0
 
     @property
@@ -1728,6 +1739,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def unit_pricing(self):
+        """Returns the price of this Part at quantity=1"""
         return self.get_price(1)
 
     def add_price_break(self, quantity, price):
@@ -1748,10 +1760,12 @@ class Part(MetadataMixin, MPTTModel):
         )
 
     def get_internal_price(self, quantity, moq=True, multiples=True, currency=None):
+        """Return the internal price of this Part at the specified quantity"""
         return common.models.get_price(self, quantity, moq, multiples, currency, break_name='internal_price_breaks')
 
     @property
     def has_internal_price_breaks(self):
+        """Return True if this Part has internal pricing information"""
         return self.internal_price_breaks.count() > 0
 
     @property
@@ -1759,11 +1773,12 @@ class Part(MetadataMixin, MPTTModel):
         """Return the associated price breaks in the correct order."""
         return self.internalpricebreaks.order_by('quantity').all()
 
-    @property
-    def internal_unit_pricing(self):
-        return self.get_internal_price(1)
-
     def get_purchase_price(self, quantity):
+        """Calculate the purchase price for this part at the specified quantity
+
+        - Looks at available supplier pricing data
+        - Calculates the price base on the closest price point
+        """
         currency = currency_code_default()
         try:
             prices = [convert_money(item.purchase_price, currency).amount for item in self.stock_items.all() if item.purchase_price]
@@ -1843,7 +1858,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @transaction.atomic
     def copy_parameters_from(self, other, **kwargs):
-
+        """Copy all parameter values from another Part instance"""
         clear = kwargs.get('clear', True)
 
         if clear:
@@ -1920,12 +1935,9 @@ class Part(MetadataMixin, MPTTModel):
         return tests
 
     def getRequiredTests(self):
-        # Return the tests which are required by this part
+        """Return the tests which are required by this part"""
         return self.getTestTemplates(required=True)
 
-    def requiredTestCount(self):
-        return self.getRequiredTests().count()
-
     @property
     def attachment_count(self):
         """Count the number of attachments for this part.
@@ -2093,6 +2105,7 @@ class Part(MetadataMixin, MPTTModel):
 
     @property
     def related_count(self):
+        """Return the number of 'related parts' which point to this Part"""
         return len(self.get_related_parts())
 
     def is_part_low_on_stock(self):
@@ -2117,9 +2130,11 @@ class PartAttachment(InvenTreeAttachment):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartAttachment model"""
         return reverse('api-part-attachment-list')
 
     def getSubdir(self):
+        """Returns the media subdirectory where part attachments are stored"""
         return os.path.join("part_files", str(self.part.id))
 
     part = models.ForeignKey(Part, on_delete=models.CASCADE,
@@ -2131,6 +2146,7 @@ class PartSellPriceBreak(common.models.PriceBreak):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartSellPriceBreak model"""
         return reverse('api-part-sale-price-list')
 
     part = models.ForeignKey(
@@ -2141,6 +2157,7 @@ class PartSellPriceBreak(common.models.PriceBreak):
     )
 
     class Meta:
+        """Metaclass providing extra model definition"""
         unique_together = ('part', 'quantity')
 
 
@@ -2149,6 +2166,7 @@ class PartInternalPriceBreak(common.models.PriceBreak):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartInternalPriceBreak model"""
         return reverse('api-part-internal-price-list')
 
     part = models.ForeignKey(
@@ -2158,6 +2176,7 @@ class PartInternalPriceBreak(common.models.PriceBreak):
     )
 
     class Meta:
+        """Metaclass providing extra model definition"""
         unique_together = ('part', 'quantity')
 
 
@@ -2176,6 +2195,7 @@ class PartStar(models.Model):
     user = models.ForeignKey(User, on_delete=models.CASCADE, verbose_name=_('User'), related_name='starred_parts')
 
     class Meta:
+        """Metaclass providing extra model definition"""
         unique_together = [
             'part',
             'user'
@@ -2195,6 +2215,7 @@ class PartCategoryStar(models.Model):
     user = models.ForeignKey(User, on_delete=models.CASCADE, verbose_name=_('User'), related_name='starred_categories')
 
     class Meta:
+        """Metaclass providing extra model definition"""
         unique_together = [
             'category',
             'user',
@@ -2216,16 +2237,17 @@ class PartTestTemplate(models.Model):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartTestTemplate model"""
         return reverse('api-part-test-template-list')
 
     def save(self, *args, **kwargs):
-
+        """Enforce 'clean' operation when saving a PartTestTemplate instance"""
         self.clean()
 
         super().save(*args, **kwargs)
 
     def clean(self):
-
+        """Clean fields for the PartTestTemplate model"""
         self.test_name = self.test_name.strip()
 
         self.validate_unique()
@@ -2320,9 +2342,11 @@ class PartParameterTemplate(models.Model):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartParameterTemplate model"""
         return reverse('api-part-parameter-template-list')
 
     def __str__(self):
+        """Return a string representation of a PartParameterTemplate instance"""
         s = str(self.name)
         if self.units:
             s += " ({units})".format(units=self.units)
@@ -2368,10 +2392,11 @@ class PartParameter(models.Model):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the PartParameter model"""
         return reverse('api-part-parameter-list')
 
     def __str__(self):
-        # String representation of a PartParameter (used in the admin interface)
+        """String representation of a PartParameter (used in the admin interface)"""
         return "{part} : {param} = {data}{units}".format(
             part=str(self.part.full_name),
             param=str(self.template.name),
@@ -2380,6 +2405,7 @@ class PartParameter(models.Model):
         )
 
     class Meta:
+        """Metaclass providing extra model definition"""
         # Prevent multiple instances of a parameter for a single part
         unique_together = ('part', 'template')
 
@@ -2391,6 +2417,7 @@ class PartParameter(models.Model):
 
     @classmethod
     def create(cls, part, template, data, save=False):
+        """Custom save method for the PartParameter class"""
         part_parameter = cls(part=part, template=template, data=data)
         if save:
             part_parameter.save()
@@ -2408,6 +2435,7 @@ class PartCategoryParameterTemplate(models.Model):
     """
 
     class Meta:
+        """Metaclass providing extra model definition"""
         constraints = [
             UniqueConstraint(fields=['category', 'parameter_template'],
                              name='unique_category_parameter_template_pair')
@@ -2438,7 +2466,7 @@ class PartCategoryParameterTemplate(models.Model):
                                      help_text=_('Default Parameter Value'))
 
 
-class BomItem(models.Model, DataImportMixin):
+class BomItem(DataImportMixin, models.Model):
     """A BomItem links a part to its component items.
 
     A part can have a BOM (bill of materials) which defines
@@ -2492,6 +2520,7 @@ class BomItem(models.Model, DataImportMixin):
 
     @staticmethod
     def get_api_url():
+        """Return the list API endpoint URL associated with the BomItem model"""
         return reverse('api-bom-list')
 
     def get_valid_parts_for_allocation(self, allow_variants=True, allow_substitutes=True):
@@ -2546,7 +2575,7 @@ class BomItem(models.Model, DataImportMixin):
         return Q(part__in=[part.pk for part in self.get_valid_parts_for_allocation()])
 
     def save(self, *args, **kwargs):
-
+        """Enforce 'clean' operation when saving a BomItem instance"""
         self.clean()
         super().save(*args, **kwargs)
 
@@ -2686,12 +2715,14 @@ class BomItem(models.Model, DataImportMixin):
             raise ValidationError({'sub_part': _('Sub part must be specified')})
 
     class Meta:
+        """Metaclass providing extra model definition"""
         verbose_name = _("BOM Item")
 
         # Prevent duplication of parent/child rows
         unique_together = ('part', 'sub_part')
 
     def __str__(self):
+        """Return a string representation of this BomItem instance"""
         return "{n} x {child} to make {parent}".format(
             parent=self.part.full_name,
             child=self.sub_part.full_name,
@@ -2788,13 +2819,14 @@ class BomItemSubstitute(models.Model):
     """
 
     class Meta:
+        """Metaclass providing extra model definition"""
         verbose_name = _("BOM Item Substitute")
 
         # Prevent duplication of substitute parts
         unique_together = ('part', 'bom_item')
 
     def save(self, *args, **kwargs):
-
+        """Enforce a full_clean when saving the BomItemSubstitute model"""
         self.full_clean()
 
         super().save(*args, **kwargs)
@@ -2814,6 +2846,7 @@ class BomItemSubstitute(models.Model):
 
     @staticmethod
     def get_api_url():
+        """Returns the list API endpoint URL associated with this model"""
         return reverse('api-bom-substitute-list')
 
     bom_item = models.ForeignKey(
@@ -2847,6 +2880,7 @@ class PartRelated(models.Model):
                                verbose_name=_('Part 2'), help_text=_('Select Related Part'))
 
     def __str__(self):
+        """Return a string representation of this Part-Part relationship"""
         return f'{self.part_1} <--> {self.part_2}'
 
     def validate(self, part_1, part_2):
diff --git a/InvenTree/part/serializers.py b/InvenTree/part/serializers.py
index 9e9f5ac7d1..4094821670 100644
--- a/InvenTree/part/serializers.py
+++ b/InvenTree/part/serializers.py
@@ -1,4 +1,4 @@
-"""JSON serializers for Part app."""
+"""DRF data serializers for Part app."""
 
 import imghdr
 from decimal import Decimal
@@ -37,10 +37,6 @@ from .models import (BomItem, BomItemSubstitute, Part, PartAttachment,
 class CategorySerializer(InvenTreeModelSerializer):
     """Serializer for PartCategory."""
 
-    def __init__(self, *args, **kwargs):
-
-        super().__init__(*args, **kwargs)
-
     def get_starred(self, category):
         """Return True if the category is directly "starred" by the current user."""
         return category in self.context.get('starred_categories', [])
@@ -54,6 +50,7 @@ class CategorySerializer(InvenTreeModelSerializer):
     starred = serializers.SerializerMethodField()
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartCategory
         fields = [
             'pk',
@@ -74,6 +71,7 @@ class CategoryTree(InvenTreeModelSerializer):
     """Serializer for PartCategory tree."""
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartCategory
         fields = [
             'pk',
@@ -86,6 +84,7 @@ class PartAttachmentSerializer(InvenTreeAttachmentSerializer):
     """Serializer for the PartAttachment class."""
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartAttachment
 
         fields = [
@@ -109,6 +108,7 @@ class PartTestTemplateSerializer(InvenTreeModelSerializer):
     key = serializers.CharField(read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartTestTemplate
 
         fields = [
@@ -142,6 +142,7 @@ class PartSalePriceSerializer(InvenTreeModelSerializer):
     price_string = serializers.CharField(source='price', read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartSellPriceBreak
         fields = [
             'pk',
@@ -172,6 +173,7 @@ class PartInternalPriceSerializer(InvenTreeModelSerializer):
     price_string = serializers.CharField(source='price', read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartInternalPriceBreak
         fields = [
             'pk',
@@ -206,6 +208,7 @@ class PartThumbSerializerUpdate(InvenTreeModelSerializer):
     image = InvenTreeAttachmentSerializerField(required=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = Part
         fields = [
             'image',
@@ -216,6 +219,7 @@ class PartParameterTemplateSerializer(InvenTreeModelSerializer):
     """JSON serializer for the PartParameterTemplate model."""
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartParameterTemplate
         fields = [
             'pk',
@@ -230,6 +234,7 @@ class PartParameterSerializer(InvenTreeModelSerializer):
     template_detail = PartParameterTemplateSerializer(source='template', many=False, read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartParameter
         fields = [
             'pk',
@@ -248,6 +253,7 @@ class PartBriefSerializer(InvenTreeModelSerializer):
     stock = serializers.FloatField(source='total_stock')
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = Part
         fields = [
             'pk',
@@ -277,10 +283,14 @@ class PartSerializer(InvenTreeModelSerializer):
     """
 
     def get_api_url(self):
+        """Return the API url associated with this serializer"""
         return reverse_lazy('api-part-list')
 
     def __init__(self, *args, **kwargs):
-        """Custom initialization method for PartSerializer, so that we can optionally pass extra fields based on the query."""
+        """Custom initialization method for PartSerializer:
+
+        - Allows us to optionally pass extra fields based on the query.
+        """
         self.starred_parts = kwargs.pop('starred_parts', [])
 
         category_detail = kwargs.pop('category_detail', False)
@@ -452,6 +462,7 @@ class PartSerializer(InvenTreeModelSerializer):
     )
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = Part
         partial = True
         fields = [
@@ -503,6 +514,7 @@ class PartRelationSerializer(InvenTreeModelSerializer):
     part_2_detail = PartSerializer(source='part_2', read_only=True, many=False)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartRelated
         fields = [
             'pk',
@@ -520,6 +532,7 @@ class PartStarSerializer(InvenTreeModelSerializer):
     username = serializers.CharField(source='user.username', read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartStar
         fields = [
             'pk',
@@ -536,6 +549,7 @@ class BomItemSubstituteSerializer(InvenTreeModelSerializer):
     part_detail = PartBriefSerializer(source='part', read_only=True, many=False)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = BomItemSubstitute
         fields = [
             'pk',
@@ -553,6 +567,7 @@ class BomItemSerializer(InvenTreeModelSerializer):
     quantity = InvenTreeDecimalField(required=True)
 
     def validate_quantity(self, quantity):
+        """Perform validation for the BomItem quantity field"""
         if quantity <= 0:
             raise serializers.ValidationError(_("Quantity must be greater than zero"))
 
@@ -584,9 +599,11 @@ class BomItemSerializer(InvenTreeModelSerializer):
     available_variant_stock = serializers.FloatField(read_only=True)
 
     def __init__(self, *args, **kwargs):
-        # part_detail and sub_part_detail serializers are only included if requested.
-        # This saves a bunch of database requests
+        """Determine if extra detail fields are to be annotated on this serializer
 
+        - part_detail and sub_part_detail serializers are only included if requested.
+        - This saves a bunch of database requests
+        """
         part_detail = kwargs.pop('part_detail', False)
         sub_part_detail = kwargs.pop('sub_part_detail', False)
         include_pricing = kwargs.pop('include_pricing', False)
@@ -609,6 +626,7 @@ class BomItemSerializer(InvenTreeModelSerializer):
 
     @staticmethod
     def setup_eager_loading(queryset):
+        """Prefetch against the provided queryset to speed up database access"""
         queryset = queryset.prefetch_related('part')
         queryset = queryset.prefetch_related('part__category')
         queryset = queryset.prefetch_related('part__stock_items')
@@ -810,6 +828,7 @@ class BomItemSerializer(InvenTreeModelSerializer):
         return purchase_price_avg
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = BomItem
         fields = [
             'allow_variants',
@@ -849,6 +868,7 @@ class CategoryParameterTemplateSerializer(InvenTreeModelSerializer):
     category_detail = CategorySerializer(source='category', many=False, read_only=True)
 
     class Meta:
+        """Metaclass defining serializer fields"""
         model = PartCategoryParameterTemplate
         fields = [
             'pk',
@@ -863,6 +883,7 @@ class PartCopyBOMSerializer(serializers.Serializer):
     """Serializer for copying a BOM from another part."""
 
     class Meta:
+        """Metaclass defining serializer fields"""
         fields = [
             'part',
             'remove_existing',
@@ -929,6 +950,7 @@ class BomImportUploadSerializer(DataFileUploadSerializer):
     TARGET_MODEL = BomItem
 
     class Meta:
+        """Metaclass defining serializer fields"""
         fields = [
             'data_file',
             'part',
@@ -948,7 +970,7 @@ class BomImportUploadSerializer(DataFileUploadSerializer):
     )
 
     def save(self):
-
+        """The uploaded data file has been validated, accept the submitted data"""
         data = self.validated_data
 
         if data.get('clear_existing_bom', False):
@@ -959,11 +981,15 @@ class BomImportUploadSerializer(DataFileUploadSerializer):
 
 
 class BomImportExtractSerializer(DataFileExtractSerializer):
-    """"""
+    """Serializer class for exatracting BOM data from an uploaded file.
+
+    The parent class DataFileExtractSerializer does most of the heavy lifting here.
+    """
 
     TARGET_MODEL = BomItem
 
     def validate_extracted_columns(self):
+        """Validate that the extracted columns are correct"""
         super().validate_extracted_columns()
 
         part_columns = ['part', 'part_name', 'part_ipn', 'part_id']
@@ -973,7 +999,7 @@ class BomImportExtractSerializer(DataFileExtractSerializer):
             raise serializers.ValidationError(_("No part column specified"))
 
     def process_row(self, row):
-
+        """Process a single row from the loaded BOM file"""
         # Skip any rows which are at a lower "level"
         level = row.get('level', None)
 
@@ -1050,7 +1076,10 @@ class BomImportSubmitSerializer(serializers.Serializer):
     items = BomItemSerializer(many=True, required=True)
 
     def validate(self, data):
+        """Validate the submitted BomItem data:
 
+        - At least one line (BomItem) is required
+        """
         items = data['items']
 
         if len(items) == 0:
@@ -1061,7 +1090,11 @@ class BomImportSubmitSerializer(serializers.Serializer):
         return data
 
     def save(self):
+        """POST: Perform final save of submitted BOM data:
 
+        - By this stage each line in the BOM has been validated
+        - Individually 'save' (create) each BomItem line
+        """
         data = self.validated_data
 
         items = data['items']
diff --git a/InvenTree/part/tasks.py b/InvenTree/part/tasks.py
index cc824e2d61..db1443042a 100644
--- a/InvenTree/part/tasks.py
+++ b/InvenTree/part/tasks.py
@@ -1,3 +1,5 @@
+"""Background task definitions for the 'part' app"""
+
 import logging
 
 from django.utils.translation import gettext_lazy as _
@@ -11,6 +13,11 @@ logger = logging.getLogger("inventree")
 
 
 def notify_low_stock(part: part.models.Part):
+    """Notify interested users that a part is 'low stock':
+
+    - Triggered when the available stock for a given part falls be low the configured threhsold
+    - A notification is delivered to any users who are 'subscribed' to this part
+    """
     name = _("Low stock notification")
     message = _(f'The available stock for {part.name} has fallen below the configured minimum level')
     context = {
diff --git a/InvenTree/part/templatetags/__init__.py b/InvenTree/part/templatetags/__init__.py
index e69de29bb2..ce063ef241 100644
--- a/InvenTree/part/templatetags/__init__.py
+++ b/InvenTree/part/templatetags/__init__.py
@@ -0,0 +1 @@
+"""Custom InvenTree template tags for HTML template rendering"""
diff --git a/InvenTree/part/templatetags/inventree_extras.py b/InvenTree/part/templatetags/inventree_extras.py
index 2cdb78d326..e48c6f89c6 100644
--- a/InvenTree/part/templatetags/inventree_extras.py
+++ b/InvenTree/part/templatetags/inventree_extras.py
@@ -106,18 +106,6 @@ def str2bool(x, *args, **kwargs):
     return InvenTree.helpers.str2bool(x)
 
 
-@register.simple_tag()
-def inrange(n, *args, **kwargs):
-    """Return range(n) for iterating through a numeric quantity."""
-    return range(n)
-
-
-@register.simple_tag()
-def multiply(x, y, *args, **kwargs):
-    """Multiply two numbers together."""
-    return InvenTree.helpers.decimal2string(x * y)
-
-
 @register.simple_tag()
 def add(x, y, *args, **kwargs):
     """Add two numbers together."""
@@ -211,16 +199,19 @@ def inventree_version(shortstring=False, *args, **kwargs):
 
 @register.simple_tag()
 def inventree_is_development(*args, **kwargs):
+    """Returns True if this is a development version of InvenTree"""
     return version.isInvenTreeDevelopmentVersion()
 
 
 @register.simple_tag()
 def inventree_is_release(*args, **kwargs):
+    """Returns True if this is a release version of InvenTree"""
     return not version.isInvenTreeDevelopmentVersion()
 
 
 @register.simple_tag()
 def inventree_docs_version(*args, **kwargs):
+    """Returns the InvenTree documentation version"""
     return version.inventreeDocsVersion()
 
 
@@ -367,6 +358,7 @@ def progress_bar(val, max_val, *args, **kwargs):
 
 @register.simple_tag()
 def get_color_theme_css(username):
+    """Return the cutsom theme .css file for the selected user"""
     user_theme_name = get_user_color_theme(username)
     # Build path to CSS sheet
     inventree_css_sheet = os.path.join('css', 'color-themes', user_theme_name + '.css')
@@ -496,7 +488,7 @@ class I18nStaticNode(StaticNode):
     """
 
     def render(self, context):  # pragma: no cover
-
+        """Render this node with the determined locale context."""
         self.original = getattr(self, 'original', None)
 
         if not self.original:
diff --git a/InvenTree/part/templatetags/status_codes.py b/InvenTree/part/templatetags/status_codes.py
index 57c9fe630f..d3811c38f5 100644
--- a/InvenTree/part/templatetags/status_codes.py
+++ b/InvenTree/part/templatetags/status_codes.py
@@ -29,6 +29,7 @@ def stock_status_label(key, *args, **kwargs):
 
 @register.simple_tag
 def stock_status_text(key, *args, **kwargs):
+    """Render the text value of a StockItem status value"""
     return mark_safe(StockStatus.text(key))
 
 
diff --git a/InvenTree/part/test_api.py b/InvenTree/part/test_api.py
index 015841f760..cade51c4fb 100644
--- a/InvenTree/part/test_api.py
+++ b/InvenTree/part/test_api.py
@@ -1,3 +1,5 @@
+"""Unit tests for the various part API endpoints"""
+
 from django.urls import reverse
 
 import PIL
@@ -11,7 +13,8 @@ from company.models import Company
 from InvenTree.api_tester import InvenTreeAPITestCase
 from InvenTree.status_codes import (BuildStatus, PurchaseOrderStatus,
                                     StockStatus)
-from part.models import BomItem, BomItemSubstitute, Part, PartCategory
+from part.models import (BomItem, BomItemSubstitute, Part, PartCategory,
+                         PartRelated)
 from stock.models import StockItem, StockLocation
 
 
@@ -40,8 +43,7 @@ class PartCategoryAPITest(InvenTreeAPITestCase):
     ]
 
     def test_category_list(self):
-
-        # List all part categories
+        """Test the PartCategoryList API endpoint"""
         url = reverse('api-part-category-list')
 
         response = self.get(url, expected_code=200)
@@ -103,10 +105,6 @@ class PartOptionsAPITest(InvenTreeAPITestCase):
         'part.add',
     ]
 
-    def setUp(self):
-
-        super().setUp()
-
     def test_part(self):
         """Test the Part API OPTIONS."""
         actions = self.getActions(reverse('api-part-list'))['POST']
@@ -207,21 +205,18 @@ class PartAPITest(InvenTreeAPITestCase):
         'part_category.add',
     ]
 
-    def setUp(self):
-        super().setUp()
-
     def test_get_categories(self):
         """Test that we can retrieve list of part categories, with various filtering options."""
         url = reverse('api-part-category-list')
 
         # Request *all* part categories
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(len(response.data), 8)
 
         # Request top-level part categories only
-        response = self.client.get(
+        response = self.get(
             url,
             {
                 'parent': 'null',
@@ -232,7 +227,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(len(response.data), 2)
 
         # Children of PartCategory<1>, cascade
-        response = self.client.get(
+        response = self.get(
             url,
             {
                 'parent': 1,
@@ -244,7 +239,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(len(response.data), 5)
 
         # Children of PartCategory<1>, do not cascade
-        response = self.client.get(
+        response = self.get(
             url,
             {
                 'parent': 1,
@@ -263,7 +258,7 @@ class PartAPITest(InvenTreeAPITestCase):
         }
 
         url = reverse('api-part-category-list')
-        response = self.client.post(url, data, format='json')
+        response = self.post(url, data, format='json')
         self.assertEqual(response.status_code, status.HTTP_201_CREATED)
 
         parent = response.data['pk']
@@ -275,19 +270,20 @@ class PartAPITest(InvenTreeAPITestCase):
                 'description': 'A sort of animal',
                 'parent': parent,
             }
-            response = self.client.post(url, data, format='json')
+            response = self.post(url, data, format='json')
             self.assertEqual(response.status_code, status.HTTP_201_CREATED)
             self.assertEqual(response.data['parent'], parent)
             self.assertEqual(response.data['name'], animal)
             self.assertEqual(response.data['pathstring'], 'Animals/' + animal)
 
         # There should be now 8 categories
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
         self.assertEqual(len(response.data), 12)
 
     def test_cat_detail(self):
+        """Test the PartCategoryDetail API endpoint"""
         url = reverse('api-part-category-detail', kwargs={'pk': 4})
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         # Test that we have retrieved the category
         self.assertEqual(response.data['description'], 'Integrated Circuits')
@@ -298,22 +294,22 @@ class PartAPITest(InvenTreeAPITestCase):
         data['name'] = 'Changing category'
         data['parent'] = None
         data['description'] = 'Changing the description'
-        response = self.client.patch(url, data, format='json')
+        response = self.patch(url, data, format='json')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(response.data['description'], 'Changing the description')
         self.assertIsNone(response.data['parent'])
 
-    def test_get_all_parts(self):
+    def test_filter_parts(self):
+        """Test part filtering using the API"""
         url = reverse('api-part-list')
         data = {'cascade': True}
-        response = self.client.get(url, data, format='json')
+        response = self.get(url, data, format='json')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(len(response.data), Part.objects.count())
 
-    def test_get_parts_by_cat(self):
-        url = reverse('api-part-list')
+        # Test filtering parts by category
         data = {'category': 2}
-        response = self.client.get(url, data, format='json')
+        response = self.get(url, data, format='json')
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
         # There should only be 2 objects in category C
@@ -322,6 +318,28 @@ class PartAPITest(InvenTreeAPITestCase):
         for part in response.data:
             self.assertEqual(part['category'], 2)
 
+    def test_filter_by_related(self):
+        """Test that we can filter by the 'related' status"""
+        url = reverse('api-part-list')
+
+        # Initially there are no relations, so this should return zero results
+        response = self.get(url, {'related': 1}, expected_code=200)
+        self.assertEqual(len(response.data), 0)
+
+        # Add some relationships
+        PartRelated.objects.create(
+            part_1=Part.objects.get(pk=1),
+            part_2=Part.objects.get(pk=2),
+        )
+
+        PartRelated.objects.create(
+            part_2=Part.objects.get(pk=1),
+            part_1=Part.objects.get(pk=3)
+        )
+
+        response = self.get(url, {'related': 1}, expected_code=200)
+        self.assertEqual(len(response.data), 2)
+
     def test_include_children(self):
         """Test the special 'include_child_categories' flag.
 
@@ -331,31 +349,31 @@ class PartAPITest(InvenTreeAPITestCase):
         data = {'category': 1, 'cascade': True}
 
         # Now request to include child categories
-        response = self.client.get(url, data, format='json')
+        response = self.get(url, data, format='json')
 
         # Now there should be 5 total parts
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(len(response.data), 3)
 
     def test_test_templates(self):
-
+        """Test the PartTestTemplate API"""
         url = reverse('api-part-test-template-list')
 
         # List ALL items
-        response = self.client.get(url)
+        response = self.get(url)
 
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(len(response.data), 7)
 
         # Request for a particular part
-        response = self.client.get(url, data={'part': 10000})
+        response = self.get(url, data={'part': 10000})
         self.assertEqual(len(response.data), 5)
 
-        response = self.client.get(url, data={'part': 10004})
+        response = self.get(url, data={'part': 10004})
         self.assertEqual(len(response.data), 7)
 
         # Try to post a new object (missing description)
-        response = self.client.post(
+        response = self.post(
             url,
             data={
                 'part': 10000,
@@ -367,7 +385,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(response.status_code, 400)
 
         # Try to post a new object (should succeed)
-        response = self.client.post(
+        response = self.post(
             url,
             data={
                 'part': 10000,
@@ -381,7 +399,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(response.status_code, status.HTTP_201_CREATED)
 
         # Try to post a new test with the same name (should fail)
-        response = self.client.post(
+        response = self.post(
             url,
             data={
                 'part': 10004,
@@ -394,7 +412,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
 
         # Try to post a new test against a non-trackable part (should fail)
-        response = self.client.post(
+        response = self.post(
             url,
             data={
                 'part': 1,
@@ -408,7 +426,7 @@ class PartAPITest(InvenTreeAPITestCase):
         """Return list of part thumbnails."""
         url = reverse('api-part-thumbs')
 
-        response = self.client.get(url)
+        response = self.get(url)
 
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
@@ -432,7 +450,7 @@ class PartAPITest(InvenTreeAPITestCase):
         """
         url = reverse('api-part-list')
 
-        response = self.client.post(url, {
+        response = self.post(url, {
             'name': 'all defaults',
             'description': 'my test part',
             'category': 1,
@@ -454,7 +472,7 @@ class PartAPITest(InvenTreeAPITestCase):
             self.user
         )
 
-        response = self.client.post(url, {
+        response = self.post(url, {
             'name': 'all defaults',
             'description': 'my test part 2',
             'category': 1,
@@ -464,7 +482,7 @@ class PartAPITest(InvenTreeAPITestCase):
         self.assertTrue(response.data['purchaseable'])
 
         # "default" values should not be used if the value is specified
-        response = self.client.post(url, {
+        response = self.post(url, {
             'name': 'all defaults',
             'description': 'my test part 2',
             'category': 1,
@@ -858,14 +876,12 @@ class PartDetailTests(InvenTreeAPITestCase):
         'part_category.add',
     ]
 
-    def setUp(self):
-        super().setUp()
-
     def test_part_operations(self):
+        """Test that Part instances can be adjusted via the API"""
         n = Part.objects.count()
 
         # Create a part
-        response = self.client.post(
+        response = self.post(
             reverse('api-part-list'),
             {
                 'name': 'my test api part',
@@ -890,7 +906,7 @@ class PartDetailTests(InvenTreeAPITestCase):
 
         # Let's change the name of the part
 
-        response = self.client.patch(url, {
+        response = self.patch(url, {
             'name': 'a new better name',
         })
 
@@ -908,14 +924,14 @@ class PartDetailTests(InvenTreeAPITestCase):
 
         # Now, try to set the name to the *same* value
         # 2021-06-22 this test is to check that the "duplicate part" checks don't do strange things
-        response = self.client.patch(url, {
+        response = self.patch(url, {
             'name': 'a new better name',
         })
 
         self.assertEqual(response.status_code, 200)
 
         # Try to remove the part
-        response = self.client.delete(url)
+        response = self.delete(url)
 
         # As the part is 'active' we cannot delete it
         self.assertEqual(response.status_code, 405)
@@ -923,7 +939,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         # So, let's make it not active
         response = self.patch(url, {'active': False}, expected_code=200)
 
-        response = self.client.delete(url)
+        response = self.delete(url)
         self.assertEqual(response.status_code, 204)
 
         # Part count should have reduced
@@ -932,7 +948,7 @@ class PartDetailTests(InvenTreeAPITestCase):
     def test_duplicates(self):
         """Check that trying to create 'duplicate' parts results in errors."""
         # Create a part
-        response = self.client.post(reverse('api-part-list'), {
+        response = self.post(reverse('api-part-list'), {
             'name': 'part',
             'description': 'description',
             'IPN': 'IPN-123',
@@ -945,7 +961,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         n = Part.objects.count()
 
         # Check that we cannot create a duplicate in a different category
-        response = self.client.post(reverse('api-part-list'), {
+        response = self.post(reverse('api-part-list'), {
             'name': 'part',
             'description': 'description',
             'IPN': 'IPN-123',
@@ -968,7 +984,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         self.assertEqual(Part.objects.count(), n)
 
         # But a different 'revision' *can* be created
-        response = self.client.post(reverse('api-part-list'), {
+        response = self.post(reverse('api-part-list'), {
             'name': 'part',
             'description': 'description',
             'IPN': 'IPN-123',
@@ -985,7 +1001,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         url = reverse('api-part-detail', kwargs={'pk': pk})
 
         # Attempt to alter the revision code
-        response = self.client.patch(
+        response = self.patch(
             url,
             {
                 'revision': 'A',
@@ -996,7 +1012,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         self.assertEqual(response.status_code, 400)
 
         # But we *can* change it to a unique revision code
-        response = self.client.patch(
+        response = self.patch(
             url,
             {
                 'revision': 'C',
@@ -1010,7 +1026,7 @@ class PartDetailTests(InvenTreeAPITestCase):
         self.assignRole('part.add')
 
         # Create a new part
-        response = self.client.post(
+        response = self.post(
             reverse('api-part-list'),
             {
                 'name': 'imagine',
@@ -1175,7 +1191,7 @@ class PartAPIAggregationTest(InvenTreeAPITestCase):
     ]
 
     def setUp(self):
-
+        """Create test data as part of setup routine"""
         super().setUp()
 
         # Ensure the part "variant" tree is correctly structured
@@ -1199,9 +1215,10 @@ class PartAPIAggregationTest(InvenTreeAPITestCase):
         StockItem.objects.create(part=self.part, quantity=400, status=StockStatus.LOST)
 
     def get_part_data(self):
+        """Helper function for retrieving part data"""
         url = reverse('api-part-list')
 
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
@@ -1397,9 +1414,6 @@ class BomItemTest(InvenTreeAPITestCase):
         'part.delete',
     ]
 
-    def setUp(self):
-        super().setUp()
-
     def test_bom_list(self):
         """Tests for the BomItem list endpoint."""
         # How many BOM items currently exist in the database?
@@ -1518,7 +1532,7 @@ class BomItemTest(InvenTreeAPITestCase):
         # Now try to create a BomItem which references itself
         data['part'] = 100
         data['sub_part'] = 100
-        self.client.post(url, data, expected_code=400)
+        self.post(url, data, expected_code=400)
 
     def test_variants(self):
         """Tests for BomItem use with variants."""
@@ -1781,20 +1795,16 @@ class PartParameterTest(InvenTreeAPITestCase):
         'params',
     ]
 
-    def setUp(self):
-
-        super().setUp()
-
     def test_list_params(self):
         """Test for listing part parameters."""
         url = reverse('api-part-parameter-list')
 
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         self.assertEqual(len(response.data), 5)
 
         # Filter by part
-        response = self.client.get(
+        response = self.get(
             url,
             {
                 'part': 3,
@@ -1805,7 +1815,7 @@ class PartParameterTest(InvenTreeAPITestCase):
         self.assertEqual(len(response.data), 3)
 
         # Filter by template
-        response = self.client.get(
+        response = self.get(
             url,
             {
                 'template': 1,
@@ -1819,7 +1829,7 @@ class PartParameterTest(InvenTreeAPITestCase):
         """Test that we can create a param via the API."""
         url = reverse('api-part-parameter-list')
 
-        response = self.client.post(
+        response = self.post(
             url,
             {
                 'part': '2',
@@ -1830,7 +1840,7 @@ class PartParameterTest(InvenTreeAPITestCase):
 
         self.assertEqual(response.status_code, 201)
 
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         self.assertEqual(len(response.data), 6)
 
@@ -1838,7 +1848,7 @@ class PartParameterTest(InvenTreeAPITestCase):
         """Tests for the PartParameter detail endpoint."""
         url = reverse('api-part-parameter-detail', kwargs={'pk': 5})
 
-        response = self.client.get(url)
+        response = self.get(url)
 
         self.assertEqual(response.status_code, 200)
 
@@ -1849,12 +1859,12 @@ class PartParameterTest(InvenTreeAPITestCase):
         self.assertEqual(data['data'], '12')
 
         # PATCH data back in
-        response = self.client.patch(url, {'data': '15'}, format='json')
+        response = self.patch(url, {'data': '15'}, format='json')
 
         self.assertEqual(response.status_code, 200)
 
         # Check that the data changed!
-        response = self.client.get(url, format='json')
+        response = self.get(url, format='json')
 
         data = response.data
 
diff --git a/InvenTree/part/test_bom_export.py b/InvenTree/part/test_bom_export.py
index 67b31a812d..d7e92d1da4 100644
--- a/InvenTree/part/test_bom_export.py
+++ b/InvenTree/part/test_bom_export.py
@@ -8,6 +8,7 @@ from InvenTree.helpers import InvenTreeTestCase
 
 
 class BomExportTest(InvenTreeTestCase):
+    """Class for performing unit testing of BOM export functionality"""
 
     fixtures = [
         'category',
@@ -19,6 +20,7 @@ class BomExportTest(InvenTreeTestCase):
     roles = 'all'
 
     def setUp(self):
+        """Perform test setup functions"""
         super().setUp()
 
         self.url = reverse('bom-download', kwargs={'pk': 100})
diff --git a/InvenTree/part/test_bom_import.py b/InvenTree/part/test_bom_import.py
index bce7ac4d2f..71f47510a1 100644
--- a/InvenTree/part/test_bom_import.py
+++ b/InvenTree/part/test_bom_import.py
@@ -18,6 +18,7 @@ class BomUploadTest(InvenTreeAPITestCase):
     ]
 
     def setUp(self):
+        """Create BOM data as part of setup routine"""
         super().setUp()
 
         self.part = Part.objects.create(
@@ -37,7 +38,7 @@ class BomUploadTest(InvenTreeAPITestCase):
             )
 
     def post_bom(self, filename, file_data, clear_existing=None, expected_code=None, content_type='text/plain'):
-
+        """Helper function for submitting a BOM file"""
         bom_file = SimpleUploadedFile(
             filename,
             file_data,
diff --git a/InvenTree/part/test_bom_item.py b/InvenTree/part/test_bom_item.py
index c17f7a845d..58c5dfb032 100644
--- a/InvenTree/part/test_bom_item.py
+++ b/InvenTree/part/test_bom_item.py
@@ -1,4 +1,6 @@
 
+"""Unit tests for the BomItem model"""
+
 from decimal import Decimal
 
 import django.core.exceptions as django_exceptions
@@ -9,6 +11,7 @@ from .models import BomItem, BomItemSubstitute, Part
 
 
 class BomItemTest(TestCase):
+    """Class for unit testing BomItem model"""
 
     fixtures = [
         'category',
@@ -22,21 +25,25 @@ class BomItemTest(TestCase):
     ]
 
     def setUp(self):
+        """Create initial data"""
         self.bob = Part.objects.get(id=100)
         self.orphan = Part.objects.get(name='Orphan')
         self.r1 = Part.objects.get(name='R_2K2_0805')
 
     def test_str(self):
+        """Test the string representation of a BOMItem"""
         b = BomItem.objects.get(id=1)
         self.assertEqual(str(b), '10 x M2x4 LPHS to make BOB | Bob | A2')
 
     def test_has_bom(self):
+        """Test the has_bom attribute"""
         self.assertFalse(self.orphan.has_bom)
         self.assertTrue(self.bob.has_bom)
 
         self.assertEqual(self.bob.bom_count, 4)
 
     def test_in_bom(self):
+        """Test BOM aggregation"""
         parts = self.bob.getRequiredParts()
 
         self.assertIn(self.orphan, parts)
@@ -44,6 +51,7 @@ class BomItemTest(TestCase):
         self.assertTrue(self.bob.check_if_part_in_bom(self.orphan))
 
     def test_used_in(self):
+        """Test that the 'used_in_count' attribute is calculated correctly"""
         self.assertEqual(self.bob.used_in_count, 1)
         self.assertEqual(self.orphan.used_in_count, 1)
 
@@ -116,6 +124,7 @@ class BomItemTest(TestCase):
         self.assertNotEqual(h1, h2)
 
     def test_pricing(self):
+        """Test BOM pricing"""
         self.bob.get_price(1)
         self.assertEqual(
             self.bob.get_bom_price_range(1, internal=True),
diff --git a/InvenTree/part/test_category.py b/InvenTree/part/test_category.py
index 8270341ce9..bdc8fcc8b2 100644
--- a/InvenTree/part/test_category.py
+++ b/InvenTree/part/test_category.py
@@ -1,3 +1,5 @@
+"""Unit tests for the PartCategory model"""
+
 from django.core.exceptions import ValidationError
 from django.test import TestCase
 
@@ -18,7 +20,7 @@ class CategoryTest(TestCase):
     ]
 
     def setUp(self):
-        # Extract some interesting categories for time-saving
+        """Extract some interesting categories for time-saving"""
         self.electronics = PartCategory.objects.get(name='Electronics')
         self.mechanical = PartCategory.objects.get(name='Mechanical')
         self.resistors = PartCategory.objects.get(name='Resistors')
@@ -111,8 +113,7 @@ class CategoryTest(TestCase):
                 self.assertEqual(len(part_parameter), 1)
 
     def test_invalid_name(self):
-        # Test that an illegal character is prohibited in a category name
-
+        """Test that an illegal character is prohibited in a category name"""
         cat = PartCategory(name='test/with/illegal/chars', description='Test category', parent=None)
 
         with self.assertRaises(ValidationError) as err:
diff --git a/InvenTree/part/test_migrations.py b/InvenTree/part/test_migrations.py
index 56b6f664ef..f3562af872 100644
--- a/InvenTree/part/test_migrations.py
+++ b/InvenTree/part/test_migrations.py
@@ -32,7 +32,7 @@ class TestForwardMigrations(MigratorTestCase):
             print(p.is_template)
 
     def test_models_exist(self):
-
+        """Test that the Part model can still be accessed at the end of schema migration"""
         Part = self.new_state.apps.get_model('part', 'part')
 
         self.assertEqual(Part.objects.count(), 5)
@@ -42,3 +42,7 @@ class TestForwardMigrations(MigratorTestCase):
             part.save()
             part.is_template = False
             part.save()
+
+        for name in ['A', 'C', 'E']:
+            part = Part.objects.get(name=name)
+            self.assertEqual(part.description, f"My part {name}")
diff --git a/InvenTree/part/test_param.py b/InvenTree/part/test_param.py
index 1db23f0be2..7a13bfa6ce 100644
--- a/InvenTree/part/test_param.py
+++ b/InvenTree/part/test_param.py
@@ -1,4 +1,4 @@
-# Tests for Part Parameters
+"""Various unit tests for Part Parameters"""
 
 import django.core.exceptions as django_exceptions
 from django.test import TestCase, TransactionTestCase
@@ -8,6 +8,7 @@ from .models import (Part, PartCategory, PartCategoryParameterTemplate,
 
 
 class TestParams(TestCase):
+    """Unit test class for testing the PartParameter model"""
 
     fixtures = [
         'location',
@@ -17,7 +18,7 @@ class TestParams(TestCase):
     ]
 
     def test_str(self):
-
+        """Test the str representation of the PartParameterTemplate model"""
         t1 = PartParameterTemplate.objects.get(pk=1)
         self.assertEqual(str(t1), 'Length (mm)')
 
@@ -28,7 +29,7 @@ class TestParams(TestCase):
         self.assertEqual(str(c1), 'Mechanical | Length | 2.8')
 
     def test_validate(self):
-
+        """Test validation for part templates"""
         n = PartParameterTemplate.objects.all().count()
 
         t1 = PartParameterTemplate(name='abcde', units='dd')
@@ -44,6 +45,7 @@ class TestParams(TestCase):
 
 
 class TestCategoryTemplates(TransactionTestCase):
+    """Test class for PartCategoryParameterTemplate model"""
 
     fixtures = [
         'location',
@@ -53,7 +55,7 @@ class TestCategoryTemplates(TransactionTestCase):
     ]
 
     def test_validate(self):
-
+        """Test that category templates are correctly applied to Part instances"""
         # Category templates
         n = PartCategoryParameterTemplate.objects.all().count()
         self.assertEqual(n, 2)
@@ -79,6 +81,7 @@ class TestCategoryTemplates(TransactionTestCase):
             'main': True,
             'parent': True,
         }
+
         # Save it with category parameters
         part.save(**{'add_category_templates': add_category_templates})
 
diff --git a/InvenTree/part/test_part.py b/InvenTree/part/test_part.py
index 0069a5e4e2..b3c0ec5aa8 100644
--- a/InvenTree/part/test_part.py
+++ b/InvenTree/part/test_part.py
@@ -15,8 +15,8 @@ from common.notifications import UIMessageNotification, storage
 from InvenTree import version
 from InvenTree.helpers import InvenTreeTestCase
 
-from .models import (Part, PartCategory, PartCategoryStar, PartStar,
-                     PartTestTemplate, rename_part_image)
+from .models import (Part, PartCategory, PartCategoryStar, PartRelated,
+                     PartStar, PartTestTemplate, rename_part_image)
 from .templatetags import inventree_extras
 
 
@@ -24,39 +24,42 @@ class TemplateTagTest(InvenTreeTestCase):
     """Tests for the custom template tag code."""
 
     def test_define(self):
+        """Test the 'define' template tag"""
         self.assertEqual(int(inventree_extras.define(3)), 3)
 
     def test_str2bool(self):
+        """Various test for the str2bool template tag"""
         self.assertEqual(int(inventree_extras.str2bool('true')), True)
         self.assertEqual(int(inventree_extras.str2bool('yes')), True)
         self.assertEqual(int(inventree_extras.str2bool('none')), False)
         self.assertEqual(int(inventree_extras.str2bool('off')), False)
 
-    def test_inrange(self):
-        self.assertEqual(inventree_extras.inrange(3), range(3))
-
-    def test_multiply(self):
-        self.assertEqual(int(inventree_extras.multiply(3, 5)), 15)
-
     def test_add(self):
+        """Test that the 'add"""
         self.assertEqual(int(inventree_extras.add(3, 5)), 8)
 
     def test_plugins_enabled(self):
+        """Test the plugins_enabled tag"""
         self.assertEqual(inventree_extras.plugins_enabled(), True)
 
     def test_inventree_instance_name(self):
+        """Test the 'instance name' setting"""
         self.assertEqual(inventree_extras.inventree_instance_name(), 'InvenTree server')
 
     def test_inventree_base_url(self):
+        """Test that the base URL tag returns correctly"""
         self.assertEqual(inventree_extras.inventree_base_url(), '')
 
     def test_inventree_is_release(self):
+        """Test that the release version check functions as expected"""
         self.assertEqual(inventree_extras.inventree_is_release(), not version.isInvenTreeDevelopmentVersion())
 
     def test_inventree_docs_version(self):
+        """Test that the documentation version template tag returns correctly"""
         self.assertEqual(inventree_extras.inventree_docs_version(), version.inventreeDocsVersion())
 
     def test_hash(self):
+        """Test that the commit hash template tag returns correctly"""
         result_hash = inventree_extras.inventree_commit_hash()
         if settings.DOCKER:  # pragma: no cover
             # Testing inside docker environment *may* return an empty git commit hash
@@ -66,6 +69,7 @@ class TemplateTagTest(InvenTreeTestCase):
             self.assertGreater(len(result_hash), 5)
 
     def test_date(self):
+        """Test that the commit date template tag returns correctly"""
         d = inventree_extras.inventree_commit_date()
         if settings.DOCKER:  # pragma: no cover
             # Testing inside docker environment *may* return an empty git commit hash
@@ -75,26 +79,33 @@ class TemplateTagTest(InvenTreeTestCase):
             self.assertEqual(len(d.split('-')), 3)
 
     def test_github(self):
+        """Test that the github URL template tag returns correctly"""
         self.assertIn('github.com', inventree_extras.inventree_github_url())
 
     def test_docs(self):
+        """Test that the documentation URL template tag returns correctly"""
         self.assertIn('inventree.readthedocs.io', inventree_extras.inventree_docs_url())
 
     def test_keyvalue(self):
+        """Test keyvalue template tag"""
         self.assertEqual(inventree_extras.keyvalue({'a': 'a'}, 'a'), 'a')
 
     def test_mail_configured(self):
+        """Test that mail configuration returns False"""
         self.assertEqual(inventree_extras.mail_configured(), False)
 
     def test_user_settings(self):
+        """Test user settings"""
         result = inventree_extras.user_settings(self.user)
         self.assertEqual(len(result), len(InvenTreeUserSetting.SETTINGS))
 
     def test_global_settings(self):
+        """Test global settings"""
         result = inventree_extras.global_settings()
         self.assertEqual(len(result), len(InvenTreeSetting.SETTINGS))
 
     def test_visible_global_settings(self):
+        """Test that hidden global settings are actually hidden"""
         result = inventree_extras.visible_global_settings()
 
         n = len(result)
@@ -122,6 +133,9 @@ class PartTest(TestCase):
     ]
 
     def setUp(self):
+        """Create some Part instances as part of init routine"""
+        super().setUp()
+
         self.r1 = Part.objects.get(name='R_2K2_0805')
         self.r2 = Part.objects.get(name='R_4K7_0603')
 
@@ -130,7 +144,7 @@ class PartTest(TestCase):
         Part.objects.rebuild()
 
     def test_tree(self):
-        # Test that the part variant tree is working properly
+        """Test that the part variant tree is working properly"""
         chair = Part.objects.get(pk=10000)
         self.assertEqual(chair.get_children().count(), 3)
         self.assertEqual(chair.get_descendant_count(), 4)
@@ -142,9 +156,23 @@ class PartTest(TestCase):
         self.assertEqual(Part.objects.filter(tree_id=chair.tree_id).count(), 5)
 
     def test_str(self):
+        """Test string representation of a Part"""
         p = Part.objects.get(pk=100)
         self.assertEqual(str(p), "BOB | Bob | A2 - Can we build it?")
 
+    def test_related(self):
+        """Test the part relationship functionality"""
+        self.assertEqual(self.r1.related_count, 0)
+        self.assertEqual(self.r2.related_count, 0)
+
+        PartRelated.objects.create(part_1=self.r1, part_2=self.r2)
+
+        self.assertEqual(self.r1.related_count, 1)
+        self.assertEqual(self.r2.related_count, 1)
+
+        self.assertTrue(self.r2 in self.r1.get_related_parts())
+        self.assertTrue(self.r1 in self.r2.get_related_parts())
+
     def test_duplicate(self):
         """Test that we cannot create a "duplicate" Part."""
         n = Part.objects.count()
@@ -198,10 +226,12 @@ class PartTest(TestCase):
             part_2.validate_unique()
 
     def test_attributes(self):
+        """Test Part attributes"""
         self.assertEqual(self.r1.name, 'R_2K2_0805')
         self.assertEqual(self.r1.get_absolute_url(), '/part/3/')
 
     def test_category(self):
+        """Test PartCategory path"""
         self.assertEqual(str(self.c1.category), 'Electronics/Capacitors - Capacitors')
 
         orphan = Part.objects.get(name='Orphan')
@@ -209,26 +239,29 @@ class PartTest(TestCase):
         self.assertEqual(orphan.category_path, '')
 
     def test_rename_img(self):
+        """Test that an image can be renamed"""
         img = rename_part_image(self.r1, 'hello.png')
         self.assertEqual(img, os.path.join('part_images', 'hello.png'))
 
     def test_stock(self):
-        # No stock of any resistors
+        """Test case where there is zero stock"""
         res = Part.objects.filter(description__contains='resistor')
         for r in res:
             self.assertEqual(r.total_stock, 0)
             self.assertEqual(r.available_stock, 0)
 
     def test_barcode(self):
+        """Test barcode format functionality"""
         barcode = self.r1.format_barcode(brief=False)
         self.assertIn('InvenTree', barcode)
         self.assertIn(self.r1.name, barcode)
 
     def test_copy(self):
+        """Test that we can 'deep copy' a Part instance"""
         self.r2.deep_copy(self.r1, image=True, bom=True)
 
     def test_sell_pricing(self):
-        # check that the sell pricebreaks were loaded
+        """Check that the sell pricebreaks were loaded"""
         self.assertTrue(self.r1.has_price_breaks)
         self.assertEqual(self.r1.price_breaks.count(), 2)
         # check that the sell pricebreaks work
@@ -236,7 +269,7 @@ class PartTest(TestCase):
         self.assertEqual(float(self.r1.get_price(10)), 1.0)
 
     def test_internal_pricing(self):
-        # check that the sell pricebreaks were loaded
+        """Check that the sell pricebreaks were loaded"""
         self.assertTrue(self.r1.has_internal_price_breaks)
         self.assertEqual(self.r1.internal_price_breaks.count(), 2)
         # check that the sell pricebreaks work
@@ -262,6 +295,7 @@ class PartTest(TestCase):
 
 
 class TestTemplateTest(TestCase):
+    """Unit test for the TestTemplate class"""
 
     fixtures = [
         'category',
@@ -271,7 +305,7 @@ class TestTemplateTest(TestCase):
     ]
 
     def test_template_count(self):
-
+        """Tests for the test template functions"""
         chair = Part.objects.get(pk=10000)
 
         # Tests for the top-level chair object (nothing above it!)
@@ -288,8 +322,7 @@ class TestTemplateTest(TestCase):
         self.assertEqual(variant.getTestTemplates(required=True).count(), 5)
 
     def test_uniqueness(self):
-        # Test names must be unique for this part and also parts above
-
+        """Test names must be unique for this part and also parts above"""
         variant = Part.objects.get(pk=10004)
 
         with self.assertRaises(ValidationError):
@@ -424,6 +457,7 @@ class PartSettingsTest(InvenTreeTestCase):
 
 
 class PartSubscriptionTests(InvenTreeTestCase):
+    """Unit tests for part 'subscription'"""
 
     fixtures = [
         'location',
@@ -432,6 +466,7 @@ class PartSubscriptionTests(InvenTreeTestCase):
     ]
 
     def setUp(self):
+        """Create category and part data as part of setup routine"""
         super().setUp()
 
         # electronics / IC / MCU
@@ -531,6 +566,7 @@ class BaseNotificationIntegrationTest(InvenTreeTestCase):
     ]
 
     def setUp(self):
+        """Add an email address as part of initialization"""
         super().setUp()
         # Add Mailadress
         EmailAddress.objects.create(user=self.user, email='test@testing.com')
@@ -568,6 +604,7 @@ class PartNotificationTest(BaseNotificationIntegrationTest):
     """Integration test for part notifications."""
 
     def test_notification(self):
+        """Test that a notification is generated"""
         self._notification_run(UIMessageNotification)
 
         # There should be 1 notification message right now
diff --git a/InvenTree/part/test_views.py b/InvenTree/part/test_views.py
index 3964fb91f5..761356a5de 100644
--- a/InvenTree/part/test_views.py
+++ b/InvenTree/part/test_views.py
@@ -8,6 +8,7 @@ from .models import Part
 
 
 class PartViewTestCase(InvenTreeTestCase):
+    """Base class for unit testing the various Part views"""
 
     fixtures = [
         'category',
@@ -21,13 +22,12 @@ class PartViewTestCase(InvenTreeTestCase):
     roles = 'all'
     superuser = True
 
-    def setUp(self):
-        super().setUp()
-
 
 class PartListTest(PartViewTestCase):
+    """Unit tests for the PartList view"""
 
     def test_part_index(self):
+        """Test that the PartIndex page returns successfully"""
         response = self.client.get(reverse('part-index'))
         self.assertEqual(response.status_code, 200)
 
@@ -38,6 +38,7 @@ class PartListTest(PartViewTestCase):
 
 
 class PartDetailTest(PartViewTestCase):
+    """Unit tests for the PartDetail view"""
 
     def test_part_detail(self):
         """Test that we can retrieve a part detail page."""
@@ -67,6 +68,7 @@ class PartDetailTest(PartViewTestCase):
         pk = 1
 
         def test_ipn_match(index_result=False, detail_result=False):
+            """Helper function for matching IPN detail view"""
             index_redirect = False
             detail_redirect = False
 
@@ -117,11 +119,12 @@ class PartQRTest(PartViewTestCase):
     """Tests for the Part QR Code AJAX view."""
 
     def test_html_redirect(self):
-        # A HTML request for a QR code should be redirected (use an AJAX request instead)
+        """A HTML request for a QR code should be redirected (use an AJAX request instead)"""
         response = self.client.get(reverse('part-qr', args=(1,)))
         self.assertEqual(response.status_code, 302)
 
     def test_valid_part(self):
+        """Test QR code response for a Part"""
         response = self.client.get(reverse('part-qr', args=(1,)), HTTP_X_REQUESTED_WITH='XMLHttpRequest')
         self.assertEqual(response.status_code, 200)
 
@@ -131,6 +134,7 @@ class PartQRTest(PartViewTestCase):
         self.assertIn('<img src=', data)
 
     def test_invalid_part(self):
+        """Test response for an invalid Part ID value"""
         response = self.client.get(reverse('part-qr', args=(9999,)), HTTP_X_REQUESTED_WITH='XMLHttpRequest')
 
         self.assertEqual(response.status_code, 200)
diff --git a/InvenTree/part/views.py b/InvenTree/part/views.py
index d73cd6c8b0..4b53b80b3a 100644
--- a/InvenTree/part/views.py
+++ b/InvenTree/part/views.py
@@ -48,10 +48,16 @@ class PartIndex(InvenTreeRoleMixin, ListView):
     context_object_name = 'parts'
 
     def get_queryset(self):
+        """Custom queryset lookup to prefetch related fields"""
         return Part.objects.all().select_related('category')
 
     def get_context_data(self, **kwargs):
+        """Returns custom context data for the PartIndex view:
 
+        - children: Number of child categories
+        - category_count: Number of child categories
+        - part_count: Number of parts contained
+        """
         context = super().get_context_data(**kwargs).copy()
 
         # View top-level categories
@@ -120,15 +126,13 @@ class PartSetCategory(AjaxUpdateView):
         }
 
         if valid:
-            self.set_category()
+            with transaction.atomic():
+                for part in self.parts:
+                    part.category = self.category
+                    part.save()
 
         return self.renderJsonResponse(request, data=data, form=self.get_form(), context=self.get_context_data())
 
-    @transaction.atomic
-    def set_category(self):
-        for part in self.parts:
-            part.set_category(self.category)
-
     def get_context_data(self):
         """Return context data for rendering in the form."""
         ctx = {}
@@ -145,6 +149,7 @@ class PartImport(FileManagementFormView):
     permission_required = 'part.add'
 
     class PartFileManager(FileManager):
+        """Import field definitions"""
         REQUIRED_HEADERS = [
             'Name',
             'Description',
@@ -338,6 +343,7 @@ class PartImport(FileManagementFormView):
 
 
 class PartImportAjax(FileManagementAjaxView, PartImport):
+    """Multi-step form wizard for importing Part data"""
     ajax_form_steps_template = [
         'part/import_wizard/ajax_part_upload.html',
         'part/import_wizard/ajax_match_fields.html',
@@ -345,6 +351,7 @@ class PartImportAjax(FileManagementAjaxView, PartImport):
     ]
 
     def validate(self, obj, form, **kwargs):
+        """Validation is performed based on the current form step"""
         return PartImport.validate(self, self.steps.current, form, **kwargs)
 
 
@@ -385,6 +392,7 @@ class PartDetail(InvenTreeRoleMixin, InvenTreePluginViewMixin, DetailView):
         return Decimal(self.request.POST.get('quantity', 1))
 
     def get_part(self):
+        """Return the Part instance associated with this view"""
         return self.get_object()
 
     def get_pricing(self, quantity=1, currency=None):
@@ -499,6 +507,7 @@ class PartDetail(InvenTreeRoleMixin, InvenTreePluginViewMixin, DetailView):
         return {'quantity': self.get_quantity()}
 
     def post(self, request, *args, **kwargs):
+        """POST action performs as a GET action"""
         self.object = self.get_object()
         kwargs['object'] = self.object
         ctx = self.get_context_data(**kwargs)
@@ -506,6 +515,8 @@ class PartDetail(InvenTreeRoleMixin, InvenTreePluginViewMixin, DetailView):
 
 
 class PartDetailFromIPN(PartDetail):
+    """Part detail view using the IPN (internal part number) of the Part as the lookup field"""
+
     slug_field = 'IPN'
     slug_url_kwarg = 'slug'
 
@@ -646,7 +657,7 @@ class PartImageSelect(AjaxUpdateView):
     ]
 
     def post(self, request, *args, **kwargs):
-
+        """Perform POST action to assign selected image to the Part instance"""
         part = self.get_object()
         form = self.get_form()
 
@@ -688,7 +699,7 @@ class BomUploadTemplate(AjaxView):
     """
 
     def get(self, request, *args, **kwargs):
-
+        """Perform a GET request to download the 'BOM upload' template"""
         export_format = request.GET.get('format', 'csv')
 
         return MakeBomTemplate(export_format)
@@ -705,7 +716,7 @@ class BomDownload(AjaxView):
     model = Part
 
     def get(self, request, *args, **kwargs):
-
+        """Perform GET request to download BOM data"""
         part = get_object_or_404(Part, pk=self.kwargs['pk'])
 
         export_format = request.GET.get('format', 'csv')
@@ -746,6 +757,7 @@ class BomDownload(AjaxView):
                          )
 
     def get_data(self):
+        """Return a cutsom message"""
         return {
             'info': 'Exported BOM'
         }
@@ -762,6 +774,7 @@ class PartDelete(AjaxDeleteView):
     success_url = '/part/'
 
     def get_data(self):
+        """Returns custom message once the part deletion has been performed"""
         return {
             'danger': _('Part was deleted'),
         }
@@ -782,6 +795,7 @@ class PartPricing(AjaxView):
         return Decimal(self.request.POST.get('quantity', 1))
 
     def get_part(self):
+        """Return the Part instance associated with this view"""
         try:
             return Part.objects.get(id=self.kwargs['pk'])
         except Part.DoesNotExist:
@@ -886,12 +900,14 @@ class PartPricing(AjaxView):
         return {'quantity': self.get_quantity()}
 
     def get(self, request, *args, **kwargs):
+        """Perform custom GET action for this view"""
         init = self.get_initials()
         qty = self.get_quantity()
+
         return self.renderJsonResponse(request, self.form_class(initial=init), context=self.get_pricing(qty))
 
     def post(self, request, *args, **kwargs):
-
+        """Perform custom POST action for this view"""
         currency = None
 
         quantity = self.get_quantity()
@@ -946,7 +962,12 @@ class CategoryDetail(InvenTreeRoleMixin, InvenTreePluginViewMixin, DetailView):
     template_name = 'part/category.html'
 
     def get_context_data(self, **kwargs):
+        """Returns custom context data for the CategoryDetail view:
 
+        - part_count: Number of parts in this category
+        - starred_directly: True if this category is starred directly by the requesting user
+        - starred: True if this category is starred by the requesting user
+        """
         context = super().get_context_data(**kwargs).copy()
 
         try:
@@ -960,18 +981,22 @@ class CategoryDetail(InvenTreeRoleMixin, InvenTreePluginViewMixin, DetailView):
         if category:
 
             # Insert "starred" information
-            context['starred'] = category.is_starred_by(self.request.user)
             context['starred_directly'] = context['starred'] and category.is_starred_by(
                 self.request.user,
                 include_parents=False,
             )
 
+            if context['starred_directly']:
+                # Save a database lookup - if 'starred_directly' is True, we know 'starred' is also
+                context['starred'] = True
+            else:
+                context['starred'] = category.is_starred_by(self.request.user)
+
         return context
 
 
 class CategoryDelete(AjaxDeleteView):
     """Delete view to delete a PartCategory."""
-
     model = PartCategory
     ajax_template_name = 'part/category_delete.html'
     ajax_form_title = _('Delete Part Category')
@@ -979,6 +1004,7 @@ class CategoryDelete(AjaxDeleteView):
     success_url = '/part/'
 
     def get_data(self):
+        """Return custom context data when the category is deleted"""
         return {
             'danger': _('Part category was deleted'),
         }
@@ -1092,6 +1118,11 @@ class CategoryParameterTemplateEdit(AjaxUpdateView):
     ajax_form_title = _('Edit Category Parameter Template')
 
     def get_object(self):
+        """Returns the PartCategoryParameterTemplate associated with this view
+
+        - First, attempt lookup based on supplied 'pid' kwarg
+        - Else, attempt lookup based on supplied 'pk' kwarg
+        """
         try:
             self.object = self.model.objects.get(pk=self.kwargs['pid'])
         except:
@@ -1148,6 +1179,11 @@ class CategoryParameterTemplateDelete(AjaxDeleteView):
     ajax_form_title = _("Delete Category Parameter Template")
 
     def get_object(self):
+        """Returns the PartCategoryParameterTemplate associated with this view
+
+        - First, attempt lookup based on supplied 'pid' kwarg
+        - Else, attempt lookup based on supplied 'pk' kwarg
+        """
         try:
             self.object = self.model.objects.get(pk=self.kwargs['pid'])
         except:
diff --git a/setup.cfg b/setup.cfg
index 3aa96371ec..76d1209188 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -15,6 +15,8 @@ ignore =
 	N806,
 	# - N812 - lowercase imported as non-lowercase
 	N812,
+	# - D202 - No blank lines allowed after function docstring
+	D202,
 	# - D415 - First line should end with a period, question mark, or exclamation point
 	D415,
 exclude = .git,__pycache__,*/migrations/*,*/lib/*,*/bin/*,*/media/*,*/static/*,InvenTree/plugins/*