code: public Observable<Page<DataMigrationServiceInner>> listByResourceGroupAsync(final String groupName) {
          return listByResourceGroupWithServiceResponseAsync(groupName)
              .map(new Func1<ServiceResponse<Page<DataMigrationServiceInner>>, Page<DataMigrationServiceInner>>() {
                  @Override
                  public Page<DataMigrationServiceInner> call(ServiceResponse<Page<DataMigrationServiceInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Get services in resource group.
  The Services resource is the top-level resource that represents the Data Migration Service. This method returns a list of service resources in a resource group.
  
  @param groupName Name of the resource group
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;DataMigrationServiceInner&gt; object