input: Write a function to implement the command-line interface for downloading 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 function should support the following commands: "download", "exist", "test", "list", "help", and "version". The function should return the appropriate output based on the command provided.
  assert main(['download', '/path/to/movie1', '/path/to/movie2', '--lang=en'])==None
  assert main(['exist', '/path/to/movie1', '--lang=en'])==None
  assert main(['test'])==None
  assert main(['--list'])==None
  assert main(['--help'])==None
  assert main(['--version'])==None
output: def main(args):
      command = args[0]
      if command == 'download':
          for path in args[1:]:
              if '--lang=' in path:
                  lang = path.split('=')[1]
              else:
                  lang = None
              # Download subtitles logic here
              pass
      elif command == 'exist':
          for path in args[1:]:
              if '--lang=' in path:
                  lang = path.split('=')[1]
              else:
                  lang = None
              # Check if subtitles exist logic here
              pass
      elif command == 'test':
          # Test logic here
          pass
      elif command == '--list':
          # List available subtitles logic here
          pass
      elif command == '--help':
          # Help message logic here
          pass
      elif command == '--version':
          # Version message logic here
          pass
      else:
          # Invalid command logic here
          pass