'A copy of this description, with all servers marked Unknown.'

def reset(self):

    if (self._topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary):
        topology_type = TOPOLOGY_TYPE.ReplicaSetNoPrimary
    else:
        topology_type = self._topology_type
    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)
