public Map<String, List<OffsetFetchRequestTopics>> groupIdsToTopics() {
        Map<String, List<OffsetFetchRequestTopics>> groupIdsToTopics =
            new HashMap<>(data.groups().size());
        data.groups().forEach(g -> groupIdsToTopics.put(g.groupId(), g.topics()));
        return groupIdsToTopics;
    }
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