protected function getItemOrCreate($id_item_base = null)
 {
     $item = null;
     if (isset($this->items[$id_item_base])) {
         $item = $this->items[$id_item_base];
     } else {
         $item = new Item();
         $item->setIdItemBase($id_item_base);
     }
     return $item;
 }