public Set<Integer> nodesThatShouldBeDown(ClusterState state) {
        return calculate(state).nodesThatShouldBeDown();
    }
@Test
    void flat_cluster_does_not_implicitly_take_down_nodes() {
        GroupAvailabilityCalculator calc = calcForFlatCluster(5, 0.99);

        assertThat(calc.nodesThatShouldBeDown(clusterState(
                "distributor:5 storage:5 .1.s:d .2.s:d")), equalTo(emptySet()));

    }