input: Write a function to provide a command-line interface to download subtitles for movies and TV shows. The function should accept one or more release paths as arguments and allow specifying the language and subtitle site to use. The function should handle commands such as "download", "exist", "test", "list", "help", and "version". If the function is invoked with the "download" command, it should print the status of each subtitle download. If the function is invoked with the "exist" command, it should print whether subtitles exist for each release path. If the function is invoked with the "test" command, it should test the specified engines. If the function is invoked with the "list" command, it should print the list of available subtitle sites. If the function is invoked with the "help" command, it should display the help screen. If the function is invoked with the "version" command, it should display the version of the script.
  assert download_subtitles(["/path/to/movie1.mkv", "/path/to/movie2.mkv"], ["opensubtitles"], "en")==None
  assert is_subtitles_exist(["/path/to/show1.mkv", "/path/to/show2.mkv"], ["subscene"], "es")==None
  assert test_engines(["opensubtitles", "subscene"])==None
  assert main(["--list"])==None
  assert main(["--help"])==None
  assert main(["--version"])==None
output: def download_subtitles(release_paths, subtitle_sites, language):
      for path in release_paths:
          print(f"Downloading subtitles for {path} from {subtitle_sites} in {language}")
  
  def is_subtitles_exist(release_paths, subtitle_sites, language):
      for path in release_paths:
          print(f"Checking if subtitles exist for {path} from {subtitle_sites} in {language}")
  
  def test_engines(subtitle_sites):
      for site in subtitle_sites:
          print(f"Testing engine for {site}")
  
  def main(args):
      if "--list" in args:
          print("Available subtitle sites: opensubtitles, subscene")
      elif "--help" in args:
          print("Help screen: This script allows downloading, checking existence, testing engines, listing sites, and displaying version.")
      elif "--version" in args:
          print("Version 1.0")