/*
* Extract the actual artist/album/track ID from a MBE_GetxxxxxId query.
*
* The MBE_GETxxxxxId queries return a URL where additional RDF metadata
* for a given ID can be retrieved. Callers may wish to extract only
* the ID of an artist/album/track for reference.
*
* Aliases:
* MusicBrainz::Client#get_id_from_url
*
* Examples:
* # get the artist name of the first track on the album
* url = mb.result MusicBrainz::Query::AlbumGetArtistId, 1
* id = mb.id_from_url url
*
*/
static VALUE mb_client_id_from_url(VALUE self, VALUE url) {