code: public Observable<VpnGatewayInner> updateTagsAsync(String resourceGroupName, String gatewayName) {
          return updateTagsWithServiceResponseAsync(resourceGroupName, gatewayName).map(new Func1<ServiceResponse<VpnGatewayInner>, VpnGatewayInner>() {
              @Override
              public VpnGatewayInner call(ServiceResponse<VpnGatewayInner> response) {
                  return response.body();
              }
          });
      }
docs: Updates virtual wan vpn gateway tags.
  
  @param resourceGroupName The resource group name of the VpnGateway.
  @param gatewayName The name of the gateway.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request