code: def item_acl(self, item):
          
          if self.es_based:
              from nefertari_guards.elasticsearch import get_es_item_acl
              return get_es_item_acl(item)
          return super(DatabaseACLMixin, self).item_acl(item)
docs: Objectify ACL if ES is used or call item.get_acl() if
          db is used.