protected function call_parent_register() {
		$parent_class = get_parent_class( $this );

		if ( ! method_exists( $parent_class, 'register' ) ) {
			return;
		}

		$rc = new ReflectionClass( $parent_class );

		// Bail if not instantiable.
		if ( ! $rc->isinstantiable() ) {
			return;
		}

		$parent = $rc->newInstance();
		$parent->register();
		$this->boxes = $parent->get_boxes();
	}