Group of Buttons. Group of [BaseButton]. The members of this group are treated like radio buttons in the sense that only one button can be pressed at the same time. Every member of the 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.