input: 
  def subtitles_client(command: str, releases_path: list, lang: str = 'en', engines: list = ['default_engine']) -> None:
      """ Provides a command-line interface to download and manage subtitles for movies and TV shows.
      The available commands are "download", "exist", "test", "list", "help", and "version".
      >>> subtitles_client('download', ['/path/to/movie1', '/path/to/movie2'], 'en', ['opensubtitles'])
      Downloading subtitles for '/path/to/movie1' using 'opensubtitles'.
      Downloading subtitles for '/path/to/movie2' using 'opensubtitles'.
      >>> subtitles_client('exist', ['/path/to/movie1'], 'en', ['opensubtitles'])
      Checking if subtitles exist for '/path/to/movie1' using 'opensubtitles'.
      """
  
output:     if command == 'download':
          for path in releases_path:
              for engine in engines:
                  print(f"Downloading subtitles for '{path}' using '{engine}'.")
      elif command == 'exist':
          for path in releases_path:
              for engine in engines:
                  print(f"Checking if subtitles exist for '{path}' using '{engine}'.")
      elif command == 'test':
          print("Running tests for subtitle engines.")
      elif command == 'list':
          print("Listing available subtitle engines.")
      elif command == 'help':
          print("Available commands: download, exist, test, list, help, version.")
      elif command == 'version':
          print("Subtitles Client version 1.0")
      else:
          print(f"Unknown command: {command}. Use 'help' to see available commands.")