sbool web_mergeNodesByFirstLabel_debug;

static void web_mergeNodesByFirstLabel(Web web) {
  web_check(web);
  new HashMap<Lisp, WebNode> index;
  for (WebNode node : web.nodes)
    if (!(node instanceof WebRelation) && nempty(node.labels)) index.put(first(node.labels), node);
  
  for (WebNode node : cloneList(web.nodes)) if (!(node instanceof WebRelation) && nempty(node.labels)) {
    WebNode n = index.get(first(node.labels));
    if (n == node) continue;
    if (web_mergeNodesByFirstLabel_debug)
      print("Collapsing: " + node + " => " + n);
    web_collapseNodeTo(node, n);
  }
  web_check(web);
}