code: public Observable<Page<UsageInner>> listAsync(final String location) {
          return listWithServiceResponseAsync(location)
              .map(new Func1<ServiceResponse<Page<UsageInner>>, Page<UsageInner>>() {
                  @Override
                  public Page<UsageInner> call(ServiceResponse<Page<UsageInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Gets, for the specified location, the current compute resource usage information as well as the limits for compute resources under the subscription.
  
  @param location The location for which resource usage is queried.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;UsageInner&gt; object