/**
  * @return string
  */
 public function __toString()
 {
     if ($this->applyFilters) {
         $result = $this->applyFilters->apply($this->toArray());
     } else {
         $protocolFactory = new Payone_Protocol_Factory();
         $defaultApplyFilters = $protocolFactory->buildServiceApplyFilters();
         $result = $defaultApplyFilters->apply($this->toArray());
     }
     return $result;
 }
 protected function _toString($aValue)
 {
     if ($this->applyFilters) {
         $result = $this->applyFilters->apply($aValue);
     } else {
         $protocolFactory = new Payone_Protocol_Factory();
         $defaultApplyFilters = $protocolFactory->buildServiceApplyFilters();
         $result = $defaultApplyFilters->apply($aValue);
     }
     return $result;
 }