private static void addMapEntries(Map<String, Node> ret, String name, Map<String, Node> map) {
        for (Map.Entry<String, Node> entry : map.entrySet())
            ret.put(name + "{" + entry.getKey() + "}", entry.getValue());
    }
Returns a flat map of this node's direct children, including all NodeVectors' elements.
Keys are the node name, including index for vector elements, e.g. 'arr[0]'.
config-lib/src/main/java/com/yahoo/config/InnerNode.java