public boolean isAllPartitionsForGroup(String groupId) {
        OffsetFetchRequestGroup group = data
            .groups()
            .stream()
            .filter(g -> g.groupId().equals(groupId))
            .collect(Collectors.toList())
            .get(0);
        return group.topics() == ALL_TOPIC_PARTITIONS_BATCH;
    }
Indicates that it is not possible to fetch consumer groups in batches with FetchOffset.
Instead consumer groups' offsets must be fetched one by one.
clients/src/main/java/org/apache/kafka/common/requests/OffsetFetchRequest.java