docs: public static int ptb2Text(Reader ptbText, Writer w) throws IOException {
      int numTokens = 0;
      PTB2TextLexer lexer = new PTB2TextLexer(ptbText);
      for (String token; (token = lexer.next()) != null; ) {
        numTokens++;
        w.write(token);
      }
      return numTokens;
    }