protected function call($method, $path, array $options = [], $needsCredentials = true)
    {
        $options['headers'][self::API_VERSION_HEADER] = $this->apiVersion;

        if ($needsCredentials) {
            $options['headers'][self::API_KEY_HEADER] = $this->credentials['key'];
        }

        return $this->client->request($method, $path, $options);
    }