public function withNumber($number, $variables = null)
    {
        if (!is_null($variables)) {
            $vars = array();
            foreach ($variables as $k => $v) {
                $vars[] = array('key' => $k, 'value' => $v);
            }
            $this->setArgument("variables", $vars);
        }
        return $this->setArgument("number", $number);
    }