input: 
  def download_subtitles(releases, engines=[DEFAULTS['subtitle_engine']], lang=DEFAULTS['subtitle_language']):
      """Download subtitles for given release paths using specified engines and language.
      >>> download_subtitles(['/path/to/movie.mp4'], engines=['engine1'], lang='en')
      """
  
output:     
      subtitles = []
      for release in releases:
          for engine in engines:
              subtitle = engine.download(release, lang)
              if subtitle:
                  subtitles.append(subtitle)
                  break
      return subtitles
  