In a group of multiple toggle buttons, only one button can be active
at a time.
Setting up groups in a cycle leads to undefined behavior.
Note that the same effect can be achieved via the [interface@Gtk.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.
Adds @self to the group of @group.
In a group of multiple toggle buttons, only one button can be active at a time.
Setting up groups in a cycle leads to undefined behavior.
Note that the same effect can be achieved via the [interface@Gtk.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.