/**
  * {@inheritdoc}
  *
  * Add .btn and .btn-default classes to buttons
  *
  * @var string $title
  * @var array  $options
  */
 public function button($title, array $options = [])
 {
     $options += ['class' => $this->config('button_class')];
     $is_btn_enabled = !isset($options['btnClass']) || isset($options['btnClass']) && $options['btnClass'];
     // always add .btn class
     if ($this->config('force_class_btn') && $is_btn_enabled) {
         $options = $this->addClass($options, 'btn');
     }
     return parent::button($title, $options);
 }