static Map<TokenAndRange> ai_createNounRefMap_1(L<TokenAndRange> tokens, Set<S> pronouns, Set<S> nouns) {
  new Map<TokenAndRange> map;
  TokenAndRange lastNoun = null;
  for (TokenAndRange t : tokens) {
    if (contains(pronouns, t.token))
      mapPut(map, t, lastNoun);
    if (contains(nouns, dropLeadingDollar(t.token)))
      lastNoun = t;
  }
  ret map;
}