public Map<String, KafkaFuture<Void>> deletedGroups() {
        Map<String, KafkaFuture<Void>> deletedGroups = new HashMap<>(futures.size());
        futures.forEach((key, future) -> deletedGroups.put(key, future));
        return deletedGroups;
    }
Return a map from group id to futures which can be used to check the status of
individual deletions.
clients/src/main/java/org/apache/kafka/clients/admin/DeleteConsumerGroupsResult.java