code: def describe_splits_ex(self, 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
docs: Parameters:
       - cfName
       - start_token
       - end_token
       - keys_per_split