public function redirectTo($url = '', $parameters = array(), $stay = false)
    {
        assert('is_string($url)');
        assert('is_array($parameters)');

        if (empty($url) && isset($_REQUEST['RelayState'])) {
            $url = $_REQUEST['RelayState'];
        }

        return OneLogin_Saml2_Utils::redirect($url, $parameters, $stay);
    }