'Query MusicBrainz to determine items missing from `album`.'

def _missing(self, album):

    item_mbids = [x.mb_trackid for x in album.items()]
    if (len([i for i in album.items()]) < album.albumtotal):
        album_info = hooks.album_for_mbid(album.mb_albumid)
        for track_info in getattr(album_info, 'tracks', []):
            if (track_info.track_id not in item_mbids):
                item = _item(track_info, album_info, album.id)
                self._log.debug(u'track    {0}    in    album    {1}', track_info.track_id, album_info.album_id)
                (yield item)
