public function getValidElementTypes(){
        return array(
            'oat\\taoQtiItem\\model\\qti\\Img',
            'oat\\taoQtiItem\\model\\qti\\Math',
            'oat\\taoQtiItem\\model\\qti\\feedback\\Feedback',
            \oat\taoQtiItem\model\qti\QtiObject::class,
            'oat\\taoQtiItem\\model\\qti\\Tooltip',
            'oat\\taoQtiItem\\model\\qti\\interaction\\Interaction',
            'oat\\taoQtiItem\\model\\qti\\RubricBlock',
            'oat\\taoQtiItem\\model\\qti\\InfoControl',
            'oat\\taoQtiItem\\model\\qti\\XInclude',
            \oat\taoQtiItem\model\qti\Table::class,
        );
    }