docs: private boolean hasVerbalAuxiliary(Tree[] kids, HashSet<String> verbalSet) {
      if (DEBUG) {
        System.err.println("Checking for verbal auxiliary");
      }
      for (Tree kid : kids) {
        if (DEBUG) {
          System.err.println("  checking in " + kid);
        }
        if (kid.isPreTerminal()) {
          Label kidLabel = kid.label();
          String tag = null;
          if (kidLabel instanceof HasTag) {
            tag = ((HasTag) kidLabel).tag();
          }
          if (tag == null) {
            tag = kid.value();
          }
          Label wordLabel = kid.firstChild().label();
          String word = null;
          if (wordLabel instanceof HasWord) {
            word = ((HasWord) wordLabel).word();
          }
          if (word == null) {
            word = wordLabel.value();
          }
  
          if (DEBUG) {
            System.err.println("Checking " + kid.value() + " head is " + word + '/' + tag);
          }
          String lcWord = word.toLowerCase();
          if (verbalTags.contains(tag) && verbalSet.contains(lcWord)) {
            if (DEBUG) {
              System.err.println("hasVerbalAuxiliary returns true");
            }
            return true;
          }
        }
      }
      if (DEBUG) {
        System.err.println("hasVerbalAuxiliary returns false");
      }
      return false;
    }