'Deletes all "unknown" entries from the cache (names with indexer_id of 0).'

def clear(self, indexerid=0):

    [sickrage.srCore.cacheDB.db.delete(x[u'doc']) for x in sickrage.srCore.cacheDB.db.all(u'scene_names', with_doc=True) if (x[u'doc'][u'indexer_id'] in [indexerid, 0])]
    for item in [self.cache[key] for (key, value) in self.cache.items() if ((value == 0) or (value == indexerid))]:
        del item
