public Set<Integer> nodesThatShouldBeDown(ClusterState state) {
        return calculate(state).nodesThatShouldBeDown();
    }
@Test
    void existing_retired_node_not_implicitly_downed_when_group_taken_down() {
        GroupAvailabilityCalculator calc = calcForHierarchicCluster(
                DistributionBuilder.withGroups(3).eachWithNodeCount(3), 0.99);
        assertThat(calc.nodesThatShouldBeDown(clusterState(
                "distributor:9 storage:9 .4.s:r .5.s:d")), equalTo(indices(3))); // _not_ {3, 4}
    }