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