def add_favorite(song)
      song_id = song.is_a?(Song) ? song.id : song
      @client.request('favorite', what: 'Song', ID: song_id)
    end
def add_favorite(song)
      song_id = song.is_a?(Song) ? song.id : song
      @client.request('favorite', what: 'Song', ID: song_id)
    end
Add song to favorites