parseLibrarySongs function
Parses songs from library.
Implementation
JsonMap parseLibrarySongs(JsonMap response) {
  final results = getLibraryContents(response, MUSIC_SHELF);
  popSongsRandomMix(results);
  return {
    'results': results,
    'parsed':
        results != null
            ? parsePlaylistItems(results['contents'] as List<JsonMap>)
            : results,
  };
}