public static function getExtraFields(){
        return array_map(function($field){
            $extra = [
                'id' => $field['id'],
                'label' => $field['label'],
                'filterable' => array_key_exists('filterable', $field) ? $field['filterable'] : false,
            ];
            if (array_key_exists('columnPosition', $field)) {
                $extra['columnPosition'] = $field['columnPosition'];
            }
            return $extra;
        }, self::_getUserExtraFields());
    }