private function request_id()
 {
     if (empty(self::$_request_id)) {
         self::$_request_id = String::uuid();
     }
     return self::$_request_id;
 }
 private function request_id()
 {
     if (empty(self::$_request_id)) {
         // Class 'String' was deprecated in CakePHP 2.7 and replaced by 'CakeText'. See also: https://github.com/robwilkerson/CakePHP-Audit-Log-Plugin/issues/41
         $UuidClass = class_exists('CakeText') ? 'CakeText' : 'String';
         self::$_request_id = $UuidClass::uuid();
     }
     return self::$_request_id;
 }