public function log_out() {
        if ($accesstoken = $this->get_accesstoken()) {
            $params = array(
                'client_id' => $this->get_clientid(),
                'client_secret' => $this->get_clientsecret(),
                'token' => $accesstoken->token
            );
            $this->reset_state();
            $this->post($this->revoke_url(), $params);
        }
        parent::log_out();
    }