public void visit(SFBool field) {
            string value = context.ReadNextToken().Text;
            switch (value) {
                case "TRUE":
                    field.Value = true;
                    break;
                case "FALSE":
                    field.Value = false;
                    break;
            }

        }
 public void visit(SFBool field) {
     throw new NotImplementedException();
 }