private function revokeTokens()
    {
        $revocations = array_filter([
            'refresh_token' => $this->session->get('refreshToken'),
            'access_token' => $this->session->get('accessToken'),
        ]);
        $url = uri_for($this->config['accounts'])
            ->withPath($this->config['revoke_url'])
            ->__toString();
        foreach ($revocations as $type => $token) {
            $this->getClient()->request('post', $url, [
                'form_params' => [
                    'token' => $token,
                    'token_type_hint' => $type,
                ],
            ]);
        }
    }