code: def remove_orphans(self, instance, **kwargs):
        
        from activity_monitor.models import Activity
        try:
          instance_content_type = ContentType.objects.get_for_model(instance)
          timeline_item = Activity.objects.get(content_type=instance_content_type, object_id=instance.pk)
          timeline_item.delete()
        except Activity.DoesNotExist:
          return
docs: When an item is deleted, first delete any Activity object that has been created
        on its behalf.