private static Predicate<Node> makePredicate(Set<String> parentHostNames) {
        Objects.requireNonNull(parentHostNames, "parentHostNames cannot be null");
        if (parentHostNames.isEmpty()) return node -> true;
        return node -> node.parentHostname().isPresent() && parentHostNames.contains(node.parentHostname().get());
    }
Creates a node filter which filters using the given parent host name
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/node/filter/ParentHostFilter.java