public function listColumns($bundle = null)
    {
        $columns = [];
        foreach ($this->_toolbox->attributes($bundle) as $name => $attr) {
            $columns[$name] = [
                'id' => $attr->get('id'),
                'bundle' => $attr->get('bundle'),
                'name' => $name,
                'type' => $attr->get('type'),
                'searchable ' => $attr->get('searchable'),
                'extra ' => $attr->get('extra'),
            ];
        }

        return $columns;
    }