code: private Tuple3<Set<Object>, Set<PathSpec>, Boolean> reduceRequests(
        final Batch<RestRequestBatchKey, Response<Object>> batch) {
      return batch.entries().stream()
        .map(Entry::getKey)
        .map(RestRequestBatchKey::getRequest)
        .reduce(Tuples.tuple(new HashSet<>(), new HashSet<>(), false),
            GetRequestGroup::reduceRequests,
            GetRequestGroup::combine);
    }
docs: Tuple3: (keys, fields, contains-batch-get)