@Override
    public void registerExtensions(@NotNull Group group, @NotNull DomExtensionsRegistrar registrar) {
      addInternalAttribute(registrar, Group.class);
      registrar.registerGenericAttributeValueChildExtension(new XmlName("keep-content"), Group.class)
        .setConverter(BooleanValueConverter.getInstance(false));
    }
@Override
    public void registerExtensions(@NotNull Group group, @NotNull DomExtensionsRegistrar registrar)