static L<Pair<WebNode>> web_relationsOfType(Web web, S type) {
  Lisp lbl = web.parseLabel(type);
  L<Pair<WebNode>> l = new L;
  for (Pair<WebNode> p : keys(web.relations))
    if (web.getRelation(p).hasLabel(lbl))
      l.add(p);
  ret l;
}