code: public static String labelList2Text(List<? extends HasWord> ptbWords) {
      List<String> words = new ArrayList<String>();
      for (HasWord hw : ptbWords) {
        words.add(hw.word());
      }
  
      return ptb2Text(words);
    }
docs: Returns a presentable version of the given PTB-tokenized words.
  Pass in a List of Words or a Document and this method will
  join the words with spaces and call {@link #ptb2Text(String)} on the
  output. This method will take the word() values to prevent additional
  text from creeping in (e.g., POS tags).
  
  @param ptbWords A list of HasWord objects
  @return A presentable version of the given PTB-tokenized words