static L<S> ai_categoriesForChatLine(S s) {
  new LinkedHashSet<S> l;
  if (matchStart("hello", s)) {
    l.add("greeting");
    if "hello robot|hello bot" l.add("greeting to robot");
  }
  if (matchStart("yes", s) || matchStart("no", s))
    l.add("yes/no answer");
  if (ai_isYesNoQuestion_1(s))
    l.add("yes/no question");
  else if (ai_isQuestion_1(s))
    l.add("question");
  if (matchStart("OK", s))
    l.add("ok line");
  if (startsWith(s, "!"))
    l.add("bot command");
  ret asList(l);
}