docs: public static String ptb2Text(String ptbText) {
      StringBuilder sb = new StringBuilder(ptbText.length()); // probably an overestimate
      PTB2TextLexer lexer = new PTB2TextLexer(new StringReader(ptbText));
      try {
        for (String token; (token = lexer.next()) != null; ) {
          sb.append(token);
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
      return sb.toString();
    }