private Map<Node, List<Allocation>> collateAllocations(Map<Node, List<Node>> nodeChildren) {
        return nodeChildren.entrySet().stream().collect(Collectors.toMap(
                Map.Entry::getKey,
                e -> e.getValue().stream()
                        .map(Node::allocation).flatMap(Optional::stream)
                        .collect(Collectors.toCollection(ArrayList::new))
        ));
    }
Computes a heuristic for each host, with a lower score indicating a higher perceived likelihood that removing
the host causes an unrecoverable state
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/CapacityChecker.java