static void web_addWebToWeb(Web web, Web w) {
  new HashMap<WebNode, WebNode> map;
  for (WebNode node : web.nodes) if (!(node instanceof WebRelation)) {
    WebNode n = cloneNodeToWeb(node, w);
    map.put(node, n);
  }
  for (Pair<WebNode> p : keys(web.relations))
    w.getRelation(assertNotNull(map.get(p.a)), assertNotNull(map.get(p.b))).addLabels(web.getRelation(p).labels);
}