def clean_stale_routes(self, peer, route_family=None):
        """Removes old routes from `peer` from `route_family` table.

        Routes/paths version number is compared with `peer`s current version
        number.
        """

        if route_family is not None:
            if route_family not in SUPPORTED_GLOBAL_RF:
                raise ValueError('Given route family %s is not supported.' %
                                 route_family)

            tables = [self._global_tables.get(route_family)]
        else:
            tables = self._global_tables.values()
        for table in tables:
            table.cleanup_paths_for_peer(peer)
Removes old routes from `peer` from `route_family` table.

        Routes/paths version number is compared with `peer`s current version
        number.