code: public Observable<ServiceResponse<ApplicationGatewayInner>> updateTagsWithServiceResponseAsync(String resourceGroupName, String applicationGatewayName) {
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (applicationGatewayName == null) {
              throw new IllegalArgumentException("Parameter applicationGatewayName is required and cannot be null.");
          }
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          final String apiVersion = "2018-04-01";
          final Map<String, String> tags = null;
          TagsObject parameters = new TagsObject();
          parameters.withTags(null);
          Observable<Response<ResponseBody>> observable = service.updateTags(resourceGroupName, applicationGatewayName, this.client.subscriptionId(), apiVersion, this.client.acceptLanguage(), parameters, this.client.userAgent());
          return client.getAzureClient().getPutOrPatchResultAsync(observable, new TypeToken<ApplicationGatewayInner>() { }.getType());
      }
docs: Updates the specified application gateway tags.
  
  @param resourceGroupName The name of the resource group.
  @param applicationGatewayName The name of the application gateway.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request