def build(self):
    sm = ScreenManager()
    sm.add_widget(MainScr(name='main'))
    sm.add_widget(Scr2(name='2'))
    sm.add_widget(Scr3(name='3'))
    sm.add_widget(Scr4(name='4'))
    sm.add_widget(Scr5(name='5'))
    return sm
def build(self):
    sm = ScreenManager()
    sm.add_widget(MainScr(name='main'))
    sm.add_widget(Scr2(name='2'))
    sm.add_widget(Scr3(name='3'))
    sm.add_widget(Scr4(name='4'))
    sm.add_widget(Scr5(name='5'))
    return sm