private static List<Node> getChildren(Map<Optional<String>, List<Node>> nodesByParent, Node host) {
        return nodesByParent.getOrDefault(Optional.of(host.hostname()), List.of());
    }
Try to allocate the preprovision cluster capacity.

@param mutableNodes represents all nodes in the node repo.  As preprovision capacity is virtually allocated
                    they are added to {@code mutableNodes}
@return the part of a cluster capacity it was unable to allocate, if any
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/HostCapacityMaintainer.java