old_contents: from api.utils.serializers.bookmarks import BookmarkedSerializerMixin
  from db.models.bookmarks import Bookmark
  
  
  class BookmarkedListMixinView(object):
      def get_serializer(self, *args, **kwargs):
          serializer_class = self.get_serializer_class()
          if not isinstance(serializer_class, BookmarkedSerializerMixin):
              return super().get_serializer(*args, **kwargs)
  
          queryset = args[0]
  
          if not queryset:
              return super().get_serializer(*args, **kwargs)
  
          object_ids = [o.id for o in queryset]
  
          # Batch-get all the bookmarks for the objects in the queryset
          # and pass them on to the serializer
          bookmarks = Bookmark.objects.filter(
              user=self.request.user,
              content_type__model=self.serializer_class.bookmarked_model,
              object_id__in=object_ids,
              enabled=True).values_list('id', flat=True)
  
          context = self.get_serializer_context()
          context['bookmarks'] = list(bookmarks)
          kwargs['context'] = context
          return serializer_class(*args, **kwargs)
  
new_contents: from api.utils.serializers.bookmarks import BookmarkedSerializerMixin
  from db.models.bookmarks import Bookmark
  
  
  class BookmarkedListMixinView(object):
      def get_serializer(self, *args, **kwargs):
          serializer_class = self.get_serializer_class()
          if not issubclass(serializer_class, BookmarkedSerializerMixin):
              return super().get_serializer(*args, **kwargs)
  
          queryset = args[0]
  
          if not queryset:
              return super().get_serializer(*args, **kwargs)
  
          object_ids = [o.id for o in queryset]
  
          # Batch-get all the bookmarks for the objects in the queryset
          # and pass them on to the serializer
          bookmarks = Bookmark.objects.filter(
              user=self.request.user,
              content_type__model=self.serializer_class.bookmarked_model,
              object_id__in=object_ids,
              enabled=True).values_list('id', flat=True)
  
          context = self.get_serializer_context()
          context['bookmarks'] = list(bookmarks)
          kwargs['context'] = context
          return serializer_class(*args, **kwargs)
  
subject: Fix bookmarked mixin check