Вместо окон черный экран

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.label import Label
from  kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition
from kivy.uix.textinput import TextInput
 
 
class MenuScreen(Screen):
    def e(self):
        self.boxlayout = BoxLayout(orientation='vertical')
        self.gridlayout = GridLayout(cols=3)
        self.backbutton = Button(text='Back')
        self.savebutton = Button(text='Save')
        self.titleinput = TextInput(hint_text='Title', multiline=False)
        self.noteinput = TextInput(hint_text='note', multiline=True)
        self.gridlayout.add_widget(self.backbutton)
        self.gridlayout.add_widget(self.titleinput)
        self.gridlayout.add_widget(self.savebutton)
        self.boxlayout.add_widget(self.gridlayout)
        self.boxlayout.add_widget(self.noteinput)
        self.backbutton.bind(on_press=self._on_press_button_new_pasword)
        self.savebutton.bind(on_press=self._on_press_button_new_pasword)
 
    def _on_press_button_new_pasword(self, *args):
        self.manager.transition.direction = 'right'
        self.manager.current = 'setting'
class SettingsScreen(Screen):
    def q(self):
        self.backbutton = Button(text = 'Back')
        self.boxlayout = BoxLayout(orientation='vertical')
        self.boxlayout.add_widget(self.backbutton)
        self.backbutton.bind(on_press=self._on_press_button_new_pasword)
    def _on_press_button_new_pasword(self, *args):
        self.manager.transition.direction = 'left'
        self.manager.current = 'menu'
class TestApp(App):
 
    def build(self):
        # Create the screen manager
        sm = ScreenManager()
        sm.add_widget(MenuScreen(name='menu'))
        sm.add_widget(SettingsScreen(name='settings'))
 
        return sm
 
if __name__ == '__main__':
    TestApp().run()