@Override
        public int compare(String o1, String o2) {
            int ret = map.get(o1).size() - map.get(o2).size();
            if (ret == 0) {
                ret = o1.compareTo(o2);
            }
            return ret;
        }
Returns true iff all consumers have an identical subscription. Also fills out the passed in
{@code consumerToOwnedPartitions} with each consumer's previously owned and still-subscribed partitions,
and the {@code partitionsWithMultiplePreviousOwners} with any partitions claimed by multiple previous owners
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractStickyAssignor.java