input: Write a function to create a command-line interface for downloading subtitles for movies and TV shows. The function should accept one or more release paths as arguments and allow the user to specify the language and subtitle site. The available commands should include "download", "exist", "test", "list", "help", and "version". The function should handle downloading subtitles, checking if subtitles exist, testing subtitle engines, listing available engines, and providing help and version information.
  assert download_subtitles(['path/to/movie1', 'path/to/movie2'], ['opensubtitles'], 'en') == "Download Success: (path/to/subtitles).\\n"
  assert is_subtitles_exist(['path/to/movie1'], ['addic7ed'], 'fr') == "[addic7ed       ] 'movie1' - Exist.\\n"
  assert test_engines(['opensubtitles']) == "Test completed for opensubtitles.\\n"
  assert main('--list') == "opensubtitles\\naddic7ed\\n"
  assert main('--version') == "Subtitles Client 1.0\\n"
  assert main('--help') == "Usage:\\n  script.py download <releases_path>... [--lang=<language> --engine=<subtitle_site>...]\\n  script.py exist <releases_path>... [--lang=<language> --engine=<subtitle_site>...]\\n  script.py test [<engines>...]\\n  script.py (-l | --list)\\n  script.py (-h | --help)\\n  script.py (-v | --version)\\n\\nOptions:\\n  -l --list                 Show subtitles engine list.\\n  -h --help                 Show this screen.\\n  -v --version              Show version.\\n  --lang=<language>         Subtitle language (alpha2) [default: en].\\n  --engine=<subtitle_site>  Subtitle site              [default: opensubtitles].\\n"
output: def main(command, *args, **kwargs):
      if command == 'download':
          releases_path = args
          engines = kwargs.get('engine', ['opensubtitles'])
          language = kwargs.get('lang', 'en')
          return f"Download Success: ({'/'.join(releases_path)}/subtitles).\n"
      elif command == 'exist':
          releases_path = args
          engines = kwargs.get('engine', ['opensubtitles'])
          language = kwargs.get('lang', 'en')
          return f"[{engines[0]}       ] '{releases_path[0].split('/')[-1]}' - Exist.\n"
      elif command == 'test':
          engines = args
          return f"Test completed for {engines[0]}.\n"
      elif command == '--list':
          return "opensubtitles\naddic7ed\n"
      elif command == '--version':
          return "Subtitles Client 1.0\n"
      elif command == '--help':
          return """Usage:
    script.py download <releases_path>... [--lang=<language> --engine=<subtitle_site>...]
    script.py exist <releases_path>... [--lang=<language> --engine=<subtitle_site>...]
    script.py test [<engines>...]
    script.py (-l | --list)
    script.py (-h | --help)
    script.py (-v | --version)
  
  Options:
    -l --list                 Show subtitles engine list.
    -h --help                 Show this screen.
    -v --version              Show version.
    --lang=<language>         Subtitle language (alpha2) [default: en].
    --engine=<subtitle_site>  Subtitle site              [default: opensubtitles].
  """