public TraceNode sort() {
        if (!isLeaf()) {
            for (TraceNode child : children) {
                child.sort();
            }
            if (!isStrict()) {
                Collections.sort(children);
            }
        }
        return this;
    }
Sort non-strict children recursively down the tree.

@return This, to allow chaining.
messagebus/src/main/java/com/yahoo/messagebus/TraceNode.java