code: public Observable<VirtualNetworkGatewayConnectionInner> getByResourceGroupAsync(String resourceGroupName, String virtualNetworkGatewayConnectionName) {
          return getByResourceGroupWithServiceResponseAsync(resourceGroupName, virtualNetworkGatewayConnectionName).map(new Func1<ServiceResponse<VirtualNetworkGatewayConnectionInner>, VirtualNetworkGatewayConnectionInner>() {
              @Override
              public VirtualNetworkGatewayConnectionInner call(ServiceResponse<VirtualNetworkGatewayConnectionInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets the specified virtual network gateway connection by resource group.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkGatewayConnectionName The name of the virtual network gateway connection.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the VirtualNetworkGatewayConnectionInner object