docs: public Observable<ServiceResponse<ExpressRouteGatewayInner>> createOrUpdateWithServiceResponseAsync(String resourceGroupName, String expressRouteGatewayName, ExpressRouteGatewayInner putExpressRouteGatewayParameters) {
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (expressRouteGatewayName == null) {
              throw new IllegalArgumentException("Parameter expressRouteGatewayName is required and cannot be null.");
          }
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          if (putExpressRouteGatewayParameters == null) {
              throw new IllegalArgumentException("Parameter putExpressRouteGatewayParameters is required and cannot be null.");
          }
          Validator.validate(putExpressRouteGatewayParameters);
          final String apiVersion = "2018-08-01";
          Observable<Response<ResponseBody>> observable = service.createOrUpdate(resourceGroupName, expressRouteGatewayName, this.client.subscriptionId(), putExpressRouteGatewayParameters, apiVersion, this.client.acceptLanguage(), this.client.userAgent());
          return client.getAzureClient().getPutOrPatchResultAsync(observable, new TypeToken<ExpressRouteGatewayInner>() { }.getType());
      }