static S webToString(Web web) {
  new L<S> out;
  new Map<WebNode, Int> index;
  for (int i = 0; i < l(web.nodes); i++) {
    out.add("Node " + (i+1) + ": " + struct(web.nodes.get(i).labels));
    index.put(web.nodes.get(i), i+1);
  }
  
  for (Pair<WebNode> p : keys(web.relations))
    out.add(index.get(p.a) + " -> " + index.get(p.b) + " = " + struct(web.relations.get(p).labels));
    
  ret fromLines(out);
}