code: public Observable<ServiceResponse<Page<VirtualNetworkUsageInner>>> listUsageWithServiceResponseAsync(final String resourceGroupName, final String virtualNetworkName) {
          return listUsageSinglePageAsync(resourceGroupName, virtualNetworkName)
              .concatMap(new Func1<ServiceResponse<Page<VirtualNetworkUsageInner>>, Observable<ServiceResponse<Page<VirtualNetworkUsageInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<VirtualNetworkUsageInner>>> call(ServiceResponse<Page<VirtualNetworkUsageInner>> page) {
                      String nextPageLink = page.body().nextPageLink();
                      if (nextPageLink == null) {
                          return Observable.just(page);
                      }
                      return Observable.just(page).concatWith(listUsageNextWithServiceResponseAsync(nextPageLink));
                  }
              });
      }
docs: Lists usage stats.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkName The name of the virtual network.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;VirtualNetworkUsageInner&gt; object