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).

def srem_if_not_exists(self, key, member, other_key, client=None):
        """
        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).
        """
        return self._srem_if_not_exists(
            keys=[key, other_key],
            args=[member],
            client=client)