Set of all currently connected servers.

        .. warning:: When connected to a replica set the value of :attr:`nodes`
          can change over time as :class:`MongoClient`'s view of the replica
          set changes. :attr:`nodes` can also be an empty set when
          :class:`MongoClient` is first instantiated and hasn't yet connected
          to any servers, or a network partition causes it to lose connection
          to all servers.

def nodes(self):
        """Set of all currently connected servers.

        .. warning:: When connected to a replica set the value of :attr:`nodes`
          can change over time as :class:`MongoClient`'s view of the replica
          set changes. :attr:`nodes` can also be an empty set when
          :class:`MongoClient` is first instantiated and hasn't yet connected
          to any servers, or a network partition causes it to lose connection
          to all servers.
        """
        description = self._topology.description
        return frozenset(s.address for s in description.known_servers)