input: Write a function to provide a command-line interface for downloading subtitles for movies and TV shows. The function should accept one or more release paths as arguments and optionally allow specifying the language and subtitle site to use. The function should support the commands "download", "exist", "test", "list", "help", and "version".
  
  
  def subtitles_client():
      args = docopt(__doc__, help=True, version='Subtitles Client %s' % __version__)
  
      if args['download']:
          download_subtitles(args['<releases_path>'], args['--engine'], args['--lang'])
      elif args['exist']:
          is_subtitles_exist(args['<releases_path>'], args['--engine'], args['--lang'])
      elif args['test']:
          test_engines(args['<engines>'])
      elif args['--list']:
          for sub_site in SUBTITLE_SITE_LIST.keys():
              sub_dict = SUBTITLE_SITE_LIST.get(sub_site)
              print sub_dict.get('class_name')
  
  
  assert subtitles_client(['download', 'path/to/movie1', 'path/to/movie2']) == None
  assert subtitles_client(['exist', 'path/to/movie1']) == None
  assert subtitles_client(['test']) == None
  assert subtitles_client(['--list']) == None
  assert subtitles_client(['--help']) == None
output: def subtitles_client():
      args = docopt(__doc__, help=True, version='Subtitles Client %s' % __version__)
  
      if args['download']:
          download_subtitles(args['<releases_path>'], args['--engine'], args['--lang'])
      elif args['exist']:
          is_subtitles_exist(args['<releases_path>'], args['--engine'], args['--lang'])
      elif args['test']:
          test_engines(args['<engines>'])
      elif args['--list']:
          for sub_site in SUBTITLE_SITE_LIST.keys():
              sub_dict = SUBTITLE_SITE_LIST.get(sub_site)
              print(sub_dict.get('class_name'))