code: public Observable<VirtualWANInner> createOrUpdateAsync(String resourceGroupName, String virtualWANName, VirtualWANInner wANParameters) {
          return createOrUpdateWithServiceResponseAsync(resourceGroupName, virtualWANName, wANParameters).map(new Func1<ServiceResponse<VirtualWANInner>, VirtualWANInner>() {
              @Override
              public VirtualWANInner call(ServiceResponse<VirtualWANInner> response) {
                  return response.body();
              }
          });
      }
docs: Creates a VirtualWAN resource if it doesn't exist else updates the existing VirtualWAN.
  
  @param resourceGroupName The resource group name of the VirtualWan.
  @param virtualWANName The name of the VirtualWAN being created or updated.
  @param wANParameters Parameters supplied to create or update VirtualWAN.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request