public function header($key, $value)
    {
        if (is_array($key) && !empty($key)) {
            foreach ($key as $k => $v) {
                $this->headers->set($k, $v);
            }
        } elseif (is_string($key) && !empty($key)) {
            $this->headers->set($key, $value);
        }
        return $this;
    }