title: How to run a Method on the exit of a kivy app
body: <p>I would like to run a Method when the user tries to exit the app , kind of like a "are you sure you want to exit" or "Do you want to save the file" type of message whenever the user tries to exit by clicking the Exit button on top of the window</p>
  
  <p>Some thing like 
  <code>on_quit: app.root.saveSession()</code></p>