code: def srem_if_not_exists(self, key, member, other_key, client=None):
          
          return self._srem_if_not_exists(
              keys=[key, other_key],
              args=[member],
              client=client)
docs: Removes ``member`` from the set ``key`` if ``other_key`` does not
          exist (i.e. is empty). Returns the number of removed elements (0 or 1).