public function addButton($label, $class = 'Button')
    {
        if (!$this->buttonset) {
            $this->buttonset = $this->add('ButtonSet', null, 'grid_buttons')->setClass('atk-actions');
        }

        return $this->buttonset
            ->add($class, 'gbtn'.count($this->elements))
            ->set($label);
    }