add_widget (object has no attribute)

я хочу в MDCard вместить MDLabel но у меня не получается, помогите реализовать

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.config import Config
from kivymd.uix.card import MDCard
from kivymd.uix.label import MDLabel
from kivymd.app import MDApp

Config.set('graphics', 'resizable', 0)
Config.set('graphics', 'width', 500)
Config.set('graphics', 'height', 300)

class MyApp(MDApp):
    def build(self):   
        grid_layout = GridLayout(cols = 5, spacing = 20, padding = 30)
        t1 = MDCard()
        grid_layout.add_widget(t1)
        grid_layout.t1.add_widget(MDLabel())
        return grid_layout

    def hello(self, instance):
        print("Нажата кнопка")

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

AttributeError: 'GridLayout' object has no attribute 't1'