A group of buttons that doesn't allow more than one button to be pressed at a time. A group of [BaseButton]-derived buttons. The buttons in a [ButtonGroup] are treated like radio buttons: No more than one button can be pressed at a time. Some types of buttons (such as [CheckBox]) may have a special appearance in this state. Every member of a [ButtonGroup] should have [member BaseButton.toggle_mode] set to [code]true[/code]. Returns an [Array] of [Button]s who have this as their [ButtonGroup] (see [member BaseButton.button_group]). Returns the current pressed button. Emitted when one of the buttons of the group is pressed.