protected function _checkProtectedFields(ModelAbstract $originalModel, ModelAbstract $newModel, array $protectedFields)
 {
     $orginalData = $originalModel->exportData();
     $newData = $newModel->exportData();
     foreach ($protectedFields as $field) {
         if ($orginalData[$field] !== $newData[$field]) {
             return false;
         }
     }
     return true;
 }