public NodeList childrenOf(String hostname) {
        NodeList children = get(hostname).map(NodeFamily::children).map(NodeList::copyOf).orElse(EMPTY);
        // Fallback, in case the parent itself is not in this list
        return children.isEmpty() ? matching(node -> node.hasParent(hostname)) : children;
    }
Returns the child nodes of the given parent node
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/NodeList.java