如何在kivy中处理多个键盘输入？

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.core.window import Window


class MyBoxLayout(BoxLayout):

    def __init__(self, **kwargs):
        super(MyBoxLayout, self).__init__(**kwargs)
        self.orientation = 'vertical'

        # 创建两个标签，用于显示按键状态
        self.label1 = Label(text='Key 1: ')
        self.label2 = Label(text='Key 2: ')

        self.add_widget(self.label1)
        self.add_widget(self.label2)

        # 绑定键盘事件
        Window.bind(on_key_down=self.on_key_down)
        Window.bind(on_key_up=self.on_key_up)

        self.keys = {'Key1': False, 'Key2': False}

    def on_key_down(self, instance, keycode, scancode, *args):
        if keycode[1] == 'a':
            self.keys['Key1'] = True
        elif keycode[1] == 'b':
            self.keys['Key2'] = True

        self.update_labels()
        return True

    def on_key_up(self, instance, keycode, *args):
        if keycode[1] == 'a':
            self.keys['Key1'] = False
        elif keycode[1] == 'b':
            self.keys['Key2'] = False

        self.update_labels()
        return True

    def update_labels(self):
        self.label1.text = 'Key 1: {}'.format('Pressed' if self.keys['Key1'] else 'Released')
        self.label2.text = 'Key 2: {}'.format('Pressed' if self.keys['Key2'] else 'Released')


class MyApp(App):

    def build(self):
        return MyBoxLayout()


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