Shut down the game and clean up.

def close(self):
    """Shut down the game and clean up."""
    if hasattr(self, "_controller") and self._controller:
      self._controller.quit()
      self._controller.close()
      self._controller = None
    self._shutdown()
    if hasattr(self, "_port") and self._port:
      portpicker.return_port(self._port)
      self._port = None
    if hasattr(self, "_tmp_dir") and os.path.exists(self._tmp_dir):
      shutil.rmtree(self._tmp_dir)