def _check_has_primary(sds):
    """Current topology type is ReplicaSetWithPrimary. Is primary still known?

    Pass in a dict of ServerDescriptions.

    Returns new topology type.
    """
    for s in sds.values():
        if s.server_type == SERVER_TYPE.RSPrimary:
            return TOPOLOGY_TYPE.ReplicaSetWithPrimary
    else:
        return TOPOLOGY_TYPE.ReplicaSetNoPrimary