/**
  * 
  * duplicate slide children
  * @param $slideID
  */
 private function duplicateChildren($slideID, $newSlideID)
 {
     $arrChildren = $this->getArrSlideChildren($slideID);
     foreach ($arrChildren as $childSlide) {
         $childSlideID = $childSlide->getID();
         //duplicate
         $duplicatedSlideID = $this->duplicateSlide($childSlideID);
         //update parent id
         $duplicatedSlide = new RevSlide();
         $duplicatedSlide->initByID($duplicatedSlideID);
         $duplicatedSlide->updateParentSlideID($newSlideID);
     }
 }