public function getAuthToken() {
        try {
            $response = $this->client->request('GET', "authenticate/accessToken", ['headers' => [
                'x-api-client-id' => $this->clientId,
                'x-api-key' => $this->apiKey
            ]]);

            $this->authToken = json_decode($response->getBody())->token;

            return $this->authToken;
        } catch (GuzzleHttp\Exception\RequestException $e) {
            $this->handleExceptionResult($e);
        }
    }