public function signOut()
    {
        // @todo Handle that the token may be expired.
        // @todo Handle and log that mpx may error on the signout.
        $this->client->request(
            'GET',
            self::SIGN_OUT_URL,
            [
                'query' => [
                    'schema' => '1.0',
                    'form' => 'json',
                    '_token' => (string) $this->tokenCachePool->getToken($this),
                ],
            ]
        );

        $this->tokenCachePool->deleteToken($this);
    }