diff --git a/backend/api/filters.py b/backend/api/filters.py
index 065bf581..c9e9dcf5 100644
--- a/backend/api/filters.py
+++ b/backend/api/filters.py
@@ -11,9 +11,11 @@ class DocumentFilter(FilterSet):
     speech2text_annotations__isnull = BooleanFilter(field_name='speech2text_annotations', method='filter_annotations')
 
     def filter_annotations(self, queryset, field_name, value):
-        queryset = queryset.annotate(num_annotations=
-            Count(field_name, filter=
-                Q(**{ f"{field_name}__user": self.request.user}) | Q(project__collaborative_annotation=True)))
+        queryset = queryset.annotate(num_annotations=Count(
+            expression=field_name,
+            filter=Q(**{f"{field_name}__user": self.request.user}) | Q(project__collaborative_annotation=True)
+            )
+        )
 
         should_have_annotations = not value
         if should_have_annotations:
diff --git a/backend/api/serializers.py b/backend/api/serializers.py
index f1ba2318..f26bb5d7 100644
--- a/backend/api/serializers.py
+++ b/backend/api/serializers.py
@@ -132,7 +132,8 @@ class ProjectSerializer(serializers.ModelSerializer):
     class Meta:
         model = Project
         fields = ('id', 'name', 'description', 'guideline', 'users', 'current_users_role', 'project_type',
-                  'updated_at', 'randomize_document_order', 'collaborative_annotation', 'single_class_classification', 'tags')
+                  'updated_at', 'randomize_document_order', 'collaborative_annotation', 'single_class_classification',
+                  'tags')
         read_only_fields = ('updated_at', 'users', 'current_users_role', 'tags')
 
 
@@ -191,7 +192,6 @@ class ProjectFilteredPrimaryKeyRelatedField(serializers.PrimaryKeyRelatedField):
 
 
 class DocumentAnnotationSerializer(serializers.ModelSerializer):
-    # label = ProjectFilteredPrimaryKeyRelatedField(queryset=Label.objects.all())
     label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
     document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
 
@@ -202,7 +202,6 @@ class DocumentAnnotationSerializer(serializers.ModelSerializer):
 
 
 class SequenceAnnotationSerializer(serializers.ModelSerializer):
-    #label = ProjectFilteredPrimaryKeyRelatedField(queryset=Label.objects.all())
     label = serializers.PrimaryKeyRelatedField(queryset=Label.objects.all())
     document = serializers.PrimaryKeyRelatedField(queryset=Document.objects.all())
 
diff --git a/backend/api/views/role.py b/backend/api/views/role.py
index 43d1cf3a..ba91b42d 100644
--- a/backend/api/views/role.py
+++ b/backend/api/views/role.py
@@ -59,4 +59,3 @@ class RoleMappingDetail(generics.RetrieveUpdateAPIView):
             super().perform_update(serializer)
         except IntegrityError:
             raise RoleAlreadyAssignedException
-
diff --git a/backend/api/views/statistics.py b/backend/api/views/statistics.py
index e9774029..0ffda23d 100644
--- a/backend/api/views/statistics.py
+++ b/backend/api/views/statistics.py
@@ -37,7 +37,7 @@ class StatisticsAPI(APIView):
 
     @staticmethod
     def _get_user_completion_data(annotation_class, annotation_filter):
-        all_annotation_objects  = annotation_class.objects.filter(annotation_filter)
+        all_annotation_objects = annotation_class.objects.filter(annotation_filter)
         set_user_data = collections.defaultdict(set)
         for ind_obj in all_annotation_objects.values('user__username', 'document__id'):
             set_user_data[ind_obj['user__username']].add(ind_obj['document__id'])
diff --git a/backend/api/views/upload/__init__.py b/backend/api/views/upload/__init__.py
index 8b137891..e69de29b 100644
--- a/backend/api/views/upload/__init__.py
+++ b/backend/api/views/upload/__init__.py
@@ -1 +0,0 @@
-
diff --git a/backend/api/views/upload/examples.py b/backend/api/views/upload/examples.py
index 0a37a676..af7ebd97 100644
--- a/backend/api/views/upload/examples.py
+++ b/backend/api/views/upload/examples.py
@@ -61,7 +61,7 @@ Text_JSONL = """
 """
 
 Offset_JSONL = """
-{"column_data": "EU rejects German call to boycott British lamb.", "column_label": [ [0, 2, "ORG"], [11, 17, "MISC"], ... ]}
+{"column_data": "EU rejects German call to boycott British lamb.", "column_label": [ [0, 2, "ORG"], ... ]}
 {"column_data": "Peter Blackburn", "column_label": [ [0, 15, "PERSON"] ]}
 {"column_data": "President Obama", "column_label": [ [10, 15, "PERSON"] ]}
 """
diff --git a/backend/api/views/user.py b/backend/api/views/user.py
index a8379c74..d82187d7 100644
--- a/backend/api/views/user.py
+++ b/backend/api/views/user.py
@@ -24,4 +24,3 @@ class Users(generics.ListAPIView):
     pagination_class = None
     filter_backends = (DjangoFilterBackend, filters.SearchFilter)
     search_fields = ('username',)
-