更改kivy.label的selected属性

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.togglebutton import ToggleButton
from kivy.uix.gridlayout import GridLayout

class CustomLabel(ToggleButton):
    def __init__(self, label_text, **kwargs):
        super().__init__(**kwargs)
        self.label = Label(text=label_text)
        self.bind(active=self.update_label)
        
    def update_label(self, instance, value):
        self.label.selected = value
        
class MyGrid(GridLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.cols = 1
        
        self.label1 = CustomLabel("Label 1")
        self.label2 = CustomLabel("Label 2")
        self.label3 = CustomLabel("Label 3")
        
        self.add_widget(self.label1)
        self.add_widget(self.label2)
        self.add_widget(self.label3)

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

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