code: public Observable<ServiceResponse<String>> supportedVpnDevicesWithServiceResponseAsync(String resourceGroupName, String virtualNetworkGatewayName) {
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (virtualNetworkGatewayName == null) {
              throw new IllegalArgumentException("Parameter virtualNetworkGatewayName 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 = "2017-10-01";
          return service.supportedVpnDevices(resourceGroupName, virtualNetworkGatewayName, this.client.subscriptionId(), apiVersion, this.client.acceptLanguage(), this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<String>>>() {
                  @Override
                  public Observable<ServiceResponse<String>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<String> clientResponse = supportedVpnDevicesDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Gets a xml format representation for supported vpn devices.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkGatewayName The name of the virtual network gateway.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the String object