public function setShowFeedback($showFeedback)
    {
        if (is_bool($showFeedback)) {
            $this->showFeedback = $showFeedback;
        } else {
            $msg = "ShowFeedback must be a boolean, '" . gettype($showFeedback) . "' given.";
            throw new InvalidArgumentException($msg);
        }
    }