code: @Override
    protected String nullability(Element element) {
      if (options.nullability()) {
        if (ElementUtil.hasNullableAnnotation(element)) {
          return " __nullable";
        }
        if (ElementUtil.isNonnull(element, parametersNonnullByDefault)) {
          return " __nonnull";
        }
      }
      return "";
    }
docs: Returns an Objective-C nullability attribute string if there is a matching JSR305 annotation,
  or an empty string.