如何在Kivy中更新按钮文本

from kivy.app import App
from kivy.uix.button import Button

class MyButton(Button):
    def update_text(self, new_text):
        self.text = new_text

class MyApp(App):
    def build(self):
        button = MyButton(text="原始文本")
        button.bind(on_release=self.update_button_text)
        return button

    def update_button_text(self, instance):
        instance.update_text("更新后的文本")

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