docs: def content_deleted(sender, instance=None, **kwargs):
      """removes content from the ES index when deleted from DB
      """
      if getattr(instance, "_index", True):
          cls = instance.get_real_instance_class()
          index = cls.search_objects.mapping.index
          doc_type = cls.search_objects.mapping.doc_type
  
          cls.search_objects.client.delete(index, doc_type, instance.id, ignore=[404])