input: 
  def download_subtitles(releases, engines=[DEFAULTS['subtitle_engine']], lang=DEFAULTS['subtitle_language']):
      """ Downloads subtitles for the given releases using the specified subtitle engines and language.
      >>> download_subtitles(['/path/to/movie.mkv'], ['opensubtitles', 'subscene'], 'en')
      ""
      >>> download_subtitles(['/path/to/another_movie.avi'], ['yifysubtitles'], 'es')
      ""
      """
  
output:     for release in releases:
          for engine in engines:
              subtitles = fetch_subtitles(release, engine, lang)
              if subtitles:
                  save_subtitles(release, subtitles)
                  break