private void deepCopy(Map<String, List<TopicPartition>> source, Map<String, List<TopicPartition>> dest) {
            dest.clear();
            for (Entry<String, List<TopicPartition>> entry: source.entrySet())
                dest.put(entry.getKey(), new ArrayList<>(entry.getValue()));
        }
Balance the current assignment using the data structures created in the assignPartitions(...) method above.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractStickyAssignor.java