docs: public static Function<String, String> WrapFunction(final String leftWrapper,
        final String rightWrapper) {
      Preconditions.checkNotNull(leftWrapper);
      Preconditions.checkNotNull(rightWrapper);
  
      return new Function<String, String>() {
        @Override
        public String apply(final String s) {
          return leftWrapper + s + rightWrapper;
        }
      };
    }