docs: public static ListSupertaggedSentence createWithUnobservedSupertags(List<String> words, List<String> pos) {
      return new ListSupertaggedSentence(WordAndPos.createExample(words, pos),
          Collections.nCopies(words.size(), Collections.<HeadedSyntacticCategory>emptyList()),
          Collections.nCopies(words.size(), Collections.<Double>emptyList()));
    }