spinner widget crashes my kivy app on start

I was working on a kivy(2.1.0) and added a spinner widget when I tried to run the app it crashed on startup. it works without the spinner widget. my code:

the .kv file:

<GridLayout>
    cols: 2
    rows: 8
    Label:
        text: "name:"
        row: 0
        col: 0
    TextInput:
        id: name
        multiline: False
        row:0
        col:1
        on_text: 
            if len(self.text.strip()) >= 31: self.text = self.text[0:30]
    Label:
        text: "description:"
        row: 1
        col: 0
    TextInput:
        id: description
        multiline: False
        row:1
        col:1
        on_text: 
            if len(self.text.strip()) >= 100: self.text = self.text[0:99]
    Spinner:
        text: "hi"
        values: ("hi1","h12")
    

my python file:

from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.spinner import Spinner


class SkinAssent(App):
    def __init__(self, **kwargs):
        super(SkinAssent, self).__init__(**kwargs)

    def build(self):
        return GridLayout()


def main():
    SkinAssent().run()


if __name__ == '__main__':
    main()

a window pops for a second up then i get this error:

   File "C:\Usersmyrc\AppData\Local\Programs\Python\Python310\lib\site-packages\kivy\lang\builder.py", line 558, in _apply_rule
     assert(rule not in self.rulectx)
 AssertionError

thanks, myrccar

I believe there is some kind of conflict with the GridLayout class. Try using a custom class. You can define a custom class:

class MyGridLayout(GridLayout):
    pass

Then use that custom class in your kv:

<MyGridLayout>
    cols: 2
    rows: 8
    Label:

and in your build() method:

def build(self):
    return MyGridLayout()