code: def _get_replica_set_members(self, selector):
          
          # Implemented here in Topology instead of MongoClient, so it can lock.
          with self._lock:
              topology_type = self._description.topology_type
              if topology_type not in (TOPOLOGY_TYPE.ReplicaSetWithPrimary,
                                       TOPOLOGY_TYPE.ReplicaSetNoPrimary):
                  return set()
  
              return set([sd.address for sd in selector(self._new_selection())])
docs: Return set of replica set member addresses.