text: from kivymd.app import MDApp
  from kivymd.uix.button import MDRectangleFlatButton
  from kivymd.uix.screen import MDScreen
  
  
  class Main(MDApp):
      def build(self):
          screen = MDScreen()
          btn = MDRectangleFlatButton(text="Hello World",
                                      pos_hint={'center_x': 0.5, 'center_y': 0.5}
                                      )
          screen.add_widget(btn)
          return screen
  
  
  Main().run()
  