private Map<String, List<TopicPartition>> deepCopy(Map<String, List<TopicPartition>> assignment) {
            Map<String, List<TopicPartition>> copy = new HashMap<>();
            deepCopy(assignment, copy);
            return copy;
        }
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