code: public static void normalizeTokens(final List<List<Token>> tokens,
        final String lang) {
      for (final List<Token> sentence : tokens) {
        Normalizer.convertNonCanonicalStrings(sentence, lang);
        Normalizer.normalizeQuotes(sentence, lang);
        Normalizer.normalizeDoubleQuotes(sentence, lang);
      }
    }
docs: Set as value of the token its normalized counterpart. Normalization is done
  following languages and corpora (Penn TreeBank, Ancora, Tiger, Tutpenn,
  etc.) conventions.
  
  @param tokens
  the tokens
  @param lang
  the language