public function user($user = null)
    {
        if ($user !== null) {
            $this->_user = $user;

            return;
        }

        if ($this->_user === false) {
            if (($session = $this->getSession()) && $session->id) {
                $this->_user = auth()->who($session);
            } else {
                $this->_user = null;
            }
        }

        return $this->_user;
    }