删除kivy中的标签

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout

class MyBoxLayout(BoxLayout):
    pass

class MyBoxLayout(BoxLayout):
    def __init__(self, **kwargs):
        super(MyBoxLayout, self).__init__(**kwargs)
        self.label = Label(text="Hello, Kivy!", id="my_label")
        self.add_widget(self.label)

class MyApp(App):
    def build(self):
        return MyBoxLayout()

class MyApp(App):
    def build(self):
        return MyBoxLayout()

    def delete_label(self):
        layout = self.root
        label = layout.ids.my_label
        layout.remove_widget(label)

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