public function getHttpClient(): ClientInterface
    {
        if (!($this->httpClient instanceof ClientInterface)) {
            if (property_exists($this, 'app') && $this->app['http_client']) {
                $this->httpClient = $this->app['http_client'];
            } else {
                $this->httpClient = new Client(['handler' => HandlerStack::create($this->getGuzzleHandler())]);
            }
        }

        return $this->httpClient;
    }