code: public static ProductPartitionTree createAdGroupTree(AdWordsServicesInterface services,
        AdWordsSession session, Long adGroupId) throws ApiException, RemoteException {
      return new ProductPartitionTree(
          ProductPartitionTreeImpl.createAdGroupTree(services, session, adGroupId));
    }
docs: Returns a new instance of this class by retrieving the product partitions of the
  specified ad group. All parameters are required.