docs: def write_playlist_file(self, localdir):
          """ Check if playlist exists in local directory. """
          path = "{0}/playlists".format(localdir)
          if not os.path.exists(path):
              os.makedirs(path)
  
          filepath = "{0}/{1}".format(path, self.gen_filename())
          playlist = open(filepath, "w")
          for track in self.get_tracks():
              playlist.write("{0}/{1}.mp3\n".format(
                  os.path.abspath(track.gen_localdir(localdir)),
                  track.gen_filename()))
          playlist.close()