private static Map<Uuid, Set<Integer>> deepCopy(Map<Uuid, Set<Integer>> map) {
        Map<Uuid, Set<Integer>> copy = new HashMap<>(map.size());
        for (Map.Entry<Uuid, Set<Integer>> entry : map.entrySet()) {
            copy.put(entry.getKey(), new HashSet<>(entry.getValue()));
        }
        return copy;
    }
Assign the unassigned partitions to the unfilled members.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/UniformHomogeneousAssignmentBuilder.java