/**
  * passthru constructor ... 
  * allows us to attach a callback method
  * @param core
  * @param callback
  */
 public function __construct(Iface $core, $callback)
 {
     parent::__construct($core);
     if (!is_callable($callback)) {
         throw $this->handle(new Exception('invalid sanitizer', $callback));
     }
     $this->sanitizer = $callback;
 }