input: Write a function to implement a command-line interface that allows users to download subtitles for movies and TV shows. The function should accept one or more release paths as arguments, and optionally, the language and subtitle site to use. The available commands are "download", "exist", "test", "list", "help", and "version". If the given command is "download", the function should attempt to download subtitles for the specified releases. If the "exist" command is used, the function should check if subtitles exist for the given releases. If the "test" command is used, the function should test the specified subtitle engines. If the "list" command is used, the function should list all available subtitle engines. If the "help" command is used, the function should display the usage information. If the "version" command is used, the function should display the version of the script.
  assert execute_command(['download', 'movie1', 'movie2'], ['--lang=en', '--engine=opensubtitles']) is None
  assert execute_command(['exist', 'movie1', 'movie2'], ['--lang=en', '--engine=opensubtitles']) is None
  assert execute_command(['test', 'opensubtitles']) is None
  assert execute_command(['--list']) is None
  assert execute_command(['--help']) is None
  assert execute_command(['--version']) is None
output: def execute_command(args, options=None):
      if args[0] == 'download':
          # Logic to download subtitles for args[1:]
          pass
      elif args[0] == 'exist':
          # Logic to check if subtitles exist for args[1:]
          pass
      elif args[0] == 'test':
          # Logic to test the specified subtitle engines
          pass
      elif args[0] == 'list':
          # Logic to list all available subtitle engines
          pass
      elif args[0] == 'help':
          # Logic to display usage information
          pass
      elif args[0] == 'version':
          # Logic to display the version of the script
          pass
      else:
          # Handle unknown command
          pass