'The (host, port) of the current primary of the replica set.
Returns ``None`` if this client is not connected to a replica set,
there is no primary, or this client was created without the
`replicaSet` option.
.. versionadded:: 3.0
MongoClient gained this property in version 3.0 when
MongoReplicaSetClient\'s functionality was merged in.'

@property
def primary(self):

    return self._topology.get_primary()
