code: public Observable<SubscriptionUsageInner> getAsync(String locationName, String usageName) {
          return getWithServiceResponseAsync(locationName, usageName).map(new Func1<ServiceResponse<SubscriptionUsageInner>, SubscriptionUsageInner>() {
              @Override
              public SubscriptionUsageInner call(ServiceResponse<SubscriptionUsageInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets a subscription usage metric.
  
  @param locationName The name of the region where the resource is located.
  @param usageName Name of usage metric to return.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the SubscriptionUsageInner object