/**
  * Get the item id for an item based on the item's sku, client id
  * and catalog id.
  * @param  Varien_Object $item
  * @return string
  */
 protected function _getItemId(Varien_Object $item)
 {
     return $this->_formatId($item->getSku(), $item->getClientId(), $item->getCatalogId());
 }