AttributeError: 'MainWindow' object has no attribute 'checkButtonGroup'

[Koussay31]

I was following along with your video, and everything worked just fine. but yesterday i got this error i cannot solve on my own

Traceback (most recent call last):
File "D:\Python Projects\StonMillia\main.py", line 50, in
window = MainWindow()
File "D:\Python Projects\StonMillia\main.py", line 28, in init
loadJsonStyle(self, self.ui)
File "C:\Users\MK323\AppData\Local\Programs\Python\Python39\lib\site-packages\Custom_Widgets_init_.py", line 207, in loadJsonStyle
applyJsonStyle(self, self.ui, data)
File "C:\Users\MK323\AppData\Local\Programs\Python\Python39\lib\site-packages\Custom_Widgets_init_.py", line 315, in applyJsonStyle
btn.clicked.connect(self.checkButtonGroup)
AttributeError: 'MainWindow' object has no attribute 'checkButtonGroup'

how to fix it