How to use the moddle.isSimpleType function in moddle

ElementHandler.prototype.handleChild = function(node) {
  var propertyDesc, type, element, childHandler;

  propertyDesc = this.getPropertyForNode(node);
  element = this.element;

  type = propertyDesc.effectiveType || propertyDesc.type;

  if (isSimpleType(type)) {
    return this.valueHandler(propertyDesc, element);
  }

  if (propertyDesc.isReference) {
    childHandler = this.referenceHandler(propertyDesc).handleNode(node);
  } else {
    childHandler = this.handler(type).handleNode(node);
  }

  var newElement = childHandler.element;

  // child handles may decide to skip elements
  // by not returning anything
  if (newElement !== undefined) {

    if (propertyDesc.isMany) {

forEach(properties, function(p) {
    var value = element.get(p.name),
        isReference = p.isReference,
        isMany = p.isMany;

    if (!isMany) {
      value = [ value ];
    }

    if (p.isBody) {
      body.push(new BodySerializer().build(p, value[0]));
    } else
    if (isSimpleType(p.type)) {
      forEach(value, function(v) {
        body.push(new ValueSerializer(self.addTagName(self.nsPropertyTagName(p))).build(p, v));
      });
    } else
    if (isReference) {
      forEach(value, function(v) {
        body.push(new ReferenceSerializer(self.addTagName(self.nsPropertyTagName(p))).build(v));
      });
    } else {
      // allow serialization via type
      // rather than element name
      var asType = serializeAsType(p),
          asProperty = serializeAsProperty(p);

      forEach(value, function(v) {
        var serializer;