public Optional<String> preferredServerAssignor(long committedOffset) {
        return serverAssignors.entrySet(committedOffset).stream()
            .max(Map.Entry.comparingByValue())
            .map(Map.Entry::getKey);
    }
@return The preferred assignor for the group with given offset.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/consumer/ConsumerGroup.java