code: public Observable<TopologyInner> getTopologyAsync(String resourceGroupName, String networkWatcherName, TopologyParameters parameters) {
          return getTopologyWithServiceResponseAsync(resourceGroupName, networkWatcherName, parameters).map(new Func1<ServiceResponse<TopologyInner>, TopologyInner>() {
              @Override
              public TopologyInner call(ServiceResponse<TopologyInner> response) {
                  return response.body();
              }
          });
      }
docs: Gets the current network topology by resource group.
  
  @param resourceGroupName The name of the resource group.
  @param networkWatcherName The name of the network watcher.
  @param parameters Parameters that define the representation of topology.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the TopologyInner object