protected function importCustomizeExtra( $rootParagraphId, $extra )
    {
        /* @var $mapper \Grid\Customize\Model\Extra\Mapper */
        $model  = $this->getSheetModel();
        $mapper = $model->getMapper()->getExtraMapper();
        $extra  = $mapper->create( array(
            'rootParagraphId'   => $rootParagraphId,
            'extra'             => $extra,
        ) );

        return $extra->save();
    }