code: public static SoyValue applyPrintDirective(
        SoyJavaPrintDirective directive, SoyValue value, List<SoyValue> args) {
      value = value == null ? NullData.INSTANCE : value;
      for (int i = 0; i < args.size(); i++) {
        if (args.get(i) == null) {
          args.set(i, NullData.INSTANCE);
        }
      }
      return directive.applyForJava(value, args);
    }
docs: Helper function to translate null -> NullData when calling SoyJavaPrintDirectives that may
  expect it.