docs: def reset(self):
          """A copy of this description, with all servers marked Unknown."""
          if self._topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary:
              topology_type = TOPOLOGY_TYPE.ReplicaSetNoPrimary
          else:
              topology_type = self._topology_type
  
          # The default ServerDescription's type is Unknown.
          sds = dict((address, ServerDescription(address))
                     for address in self._server_descriptions)
  
          return TopologyDescription(
              topology_type,
              sds,
              self._replica_set_name,
              self._max_set_version,
              self._max_election_id,
              self._topology_settings)