public Map<Integer, List<Integer>> replicasAssignments() {
        return replicasAssignments;
    }
@Test
    public void testUnmodifiableReplicasAssignments() {
        Map<Integer, List<Integer>> replicasAssignments = new HashMap<>();
        replicasAssignments.put(0, BROKER_IDS);
        NewTopic newTopic = new NewTopic(TEST_TOPIC, replicasAssignments);
        Map<Integer, List<Integer>> returnedAssignments = newTopic.replicasAssignments();

        assertThrows(UnsupportedOperationException.class, () ->
                returnedAssignments.put(1, Arrays.asList(3, 4))
        );
    }