code: def filter(self, destination_object=None, source_object=None, **kwargs):
          
          if destination_object:
              kwargs.update({
                  "destination_id": destination_object.pk,
                  "destination_type": get_for_model(destination_object),
              })
          if source_object:
              kwargs.update({
                  "source_id": source_object.pk,
                  "source_type": get_for_model(source_object),
              })
          return super(RelatedContentQuerySet, self).filter(**kwargs)
docs: See ``QuerySet.filter`` for full documentation
  
          This adds support for ``destination_object`` and ``source_object``
          as kwargs.  This converts those objects into the values necessary
          to handle the ``GenericForeignKey`` fields.