docs: def describe_ring(self, keyspace):
      """
      get the token ring: a map of ranges to host addresses,
      represented as a set of TokenRange instead of a map from range
      to list of endpoints, because you can't use Thrift structs as
      map keys:
      https://issues.apache.org/jira/browse/THRIFT-162
  
      for the same reason, we can't return a set here, even though
      order is neither important nor predictable.
  
      Parameters:
       - keyspace
      """
      self._seqid += 1
      d = self._reqs[self._seqid] = defer.Deferred()
      self.send_describe_ring(keyspace)
      return d