code: private String addHeadWordsToTreebank(final List<String> inputTrees) {
      final StringBuffer parsedDoc = new StringBuffer();
      for (final String parseSent : inputTrees) {
        final Parse parsedSentence = Parse.parseParse(parseSent);
        this.headFinder.printHeads(parsedSentence);
        parsedSentence.show(parsedDoc);
        parsedDoc.append("\n");
      }
      return parsedDoc.toString();
    }
docs: Takes as input a list of parse strings, one for line, and annotates the
  headwords
  
  @param inputTrees
  @return a list of parse trees with headwords annotated