code: def ask_folder(message='Select folder.', default='', title=''):
      
      return backend_api.opendialog("ask_folder", dict(message=message, default=default, title=title))
docs: A dialog to get a directory name.
      Returns the name of a directory, or None if user chose to cancel.
      If the "default" argument specifies a directory name, and that
      directory exists, then the dialog box will start with that directory.
  
      :param message: message to be displayed.
      :param title: window title
      :param default: default folder path
      :rtype: None or string