static WebTree webTree_sortChildrenByRelationText(WebTree tree) {
  sortList(tree.children, makeComparator(func(Pair<WebNode, WebTree> a, Pair<WebNode, WebTree> b) {
    stdCompare(web_text(a.a), web_text(b.a))
  }));
  for (Pair<WebNode, WebTree> p : tree.children)
    webTree_sortChildrenByRelationText(p.b);
  ret tree;
}