How to Create a Back Button in Kivy

I created a back button by first setting up an __init__ function in my App class and then having self.previous_screen that would hold the name of the previous screen. I used <Screen> in the .kv file to make this apply to all the screens. Then whenever I created a back button, I would reference app.previous_screen.

The main.py file:

from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.app import App, Builder

Builder.load_file("medium.kv")

class Home(Screen):
    pass
class User(Screen):
    pass

class RootWidget(ScreenManager):
    pass

class Test(App):
    def __init__(self, **kwargs):
        super(Test, self).__init__(**kwargs)
        self.previous_screen = "" 

    def build(self):
        return RootWidget()

if __name__ == '__main__':
    Test().run()

I used <Screen> and the on_leave property to make sure that the self.previous_screen updated after every screen change.

<Screen>:
    on_leave: app.previous_screen = self.name

<Home>:
    name: "home_screen"
    GridLayout:
        cols: 1
        padding: 10
        Button:
            text: "To User Screen"
            on_release: root.manager.current = "user_screen"

<User>:
    name: "user_screen"
    GridLayout:
        cols: 1
        padding: 10
        Button:
            text: "Back"
            on_release: root.manager.current = app.previous_screen

<RootWidget>:
    Home
    User