/**
  * get tax class of this product
  * 
  * @return tpyTaxClass
  */
 public function getTaxClass()
 {
     return tpyTaxClassTable::getInstance()->findOneById($this->getFrozen('tax_class_id'));
 }
 /**
  * get tax class of this product
  * 
  * @return tpyTaxClass
  */
 public function getTaxClass()
 {
     return tpyTaxClassTable::getInstance()->findOneById($this->getProductAttribute('tax_class_id'));
 }