def describe_splits_ex(self, cfName, start_token, end_token, keys_per_split):
    """
    Parameters:
     - cfName
     - start_token
     - end_token
     - keys_per_split
    """
    self._seqid += 1
    d = self._reqs[self._seqid] = defer.Deferred()
    self.send_describe_splits_ex(cfName, start_token, end_token, keys_per_split)
    return d