code: public ServiceFuture<List<DataMigrationServiceInner>> listByResourceGroupAsync(final String groupName, final ListOperationCallback<DataMigrationServiceInner> serviceCallback) {
          return AzureServiceFuture.fromPageResponse(
              listByResourceGroupSinglePageAsync(groupName),
              new Func1<String, Observable<ServiceResponse<Page<DataMigrationServiceInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<DataMigrationServiceInner>>> call(String nextPageLink) {
                      return listByResourceGroupNextSinglePageAsync(nextPageLink);
                  }
              },
              serviceCallback);
      }
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
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object