static LS gazelle_applicableHelperLists(S ruleText) {
  MultiMap<S> wordToHelperList = gazelle_wordToHelperListMultiMap();
  new Map<S, Set<S>> wordsSeenFromList;
  for (S word : words2(ruleText))
    for (S list : wordToHelperList.get(word))
      getOrCreateCISet(wordsSeenFromList, list).add(word);
  ret keysWithMultiValues(wordsSeenFromList);
}