def delete_song(cls, song_id):
song = Song().get(song_id, links=True)
if song is None:
raise NotFoundException()
# remove the song from storage first
song.remove()
# deleting a song also deletes all the associated versions
for v in song.versions:
version = Version().get(v, links=True)
version.remove()
# then remove the singer and re-index any related objects
SongIndex.delete_by_id(song.id)
