CheckButton.setGroup

Adds self to the group of group.

In a group of multiple check buttons, only one button can be active at a time. The behavior of a checkbutton in a group is also commonly known as a radio button.

Setting the group of a check button also changes the css name of the indicator widget's CSS node to 'radio'.

Setting up groups in a cycle leads to undefined behavior.

Note that the same effect can be achieved via the [gtk.actionable.Actionable] API, by using the same action with parameter type and state type 's' for all buttons in the group, and giving each button its own target value.