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