How to exit simple_menu?

I'm trying to use the simple_menu in one of apps. As a first test I wanted to display some menu entries and just close the menu on_select. but whenever I am calling the simple_menus exit() function I just get a message saying: menu has crashed. Is this a bug or am I just too stupid to understand the documentation 💁? here is what i tried: https://github.com/christian-draeger/card10-berlin-uhr/blob/master/init.py#L267