Why Kivy checkbox active event not work?

I can not find which is the main event for the checkbox in the kv file. I tried on_checkbox_active but raise an error. I tried on_active but does nothing (and do not raise any error) on_release, on_press but obviously give me an error.

this is my basic test code line: on_active: print("hello")

What is the event that run when click on a checkbox?

thank you guys