def get_albums(tracks):
    """
        Returns a dict where:
            key: album_id
            value: list of track ids
    """
    albums = {}
    for _,row in tracks.iterrows():
        album = row['album'][1:-1]
        if album != '' and album != 'None':
            if album in albums:
                albums[album].append(row['track_id'])
            else:
                albums[album] = [row['track_id']]
    return albums