public function __construct($arguments = null)
 {
     parent::__construct(array('id' => Mage::getModel('owebia_shipping2/Os2_Data_Quote')->customer_id));
 }
 protected function _getAttribute($attribute_name)
 {
     switch ($attribute_name) {
         case 'weight':
             return (double) parent::_getAttribute($attribute_name);
         default:
             return parent::_getAttribute($attribute_name);
     }
 }