I am currently trying to implement a toggle button in my KivyMD app, yet cannot make it work.
I tried running the example shown in the documentation, however I constantly receive the error AttributeError: 'ThemeManager' object has no attribute 'primary_dark'.
Even after replacing the MDRectangleFlatButton class with the normal MDButton class or removing the line self.background_down = self.theme_cls.primary_light this error still prevails.

The bug has been posted on the official GitHub (here and there) yet both issues were closed without a solution or an answer.

Has anyone found a working solution for toggle buttons?
Answers are highly appreciated.

The documentation’s example:

from kivy.lang import Builder

from kivymd.app import MDApp
from kivymd.uix.behaviors.toggle_behavior import MDToggleButton
from kivymd.uix.button import MDFlatButton

KV = '''
MDScreen:

    MDBoxLayout:
        adaptive_size: True
        spacing: "12dp"
        pos_hint: {"center_x": .5, "center_y": .5}

        MyToggleButton:
            text: "Show ads"
            group: "x"

        MyToggleButton:
            text: "Do not show ads"
            group: "x"

        MyToggleButton:
            text: "Does not matter"
            group: "x"
'''


class MyToggleButton(MDFlatButton, MDToggleButton):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.background_down = self.theme_cls.primary_color


class Test(MDApp):
    def build(self):
        self.theme_cls.theme_style = "Dark"
        self.theme_cls.primary_palette = "Orange"
        return Builder.load_string(KV)


Test().run()