The source code

    /**
     * @ignore
     * 里层包裹层定义， 适合mask以及shim
     * @author yiminghe@gmail.com
     */
    KISSY.add("component/extension/content-box", function () {

        /**
         * @class KISSY.Component.Extension.ContentBox
         * ContentBox extension class. Represent inner element of component's root element.
         */
        function ContentBox() {
        }

        ContentBox.ATTRS = {

            /**
             * content box's element of component.
             * @type {KISSY.NodeList}
             * @readonly
             * @property contentEl
             */
            /**
             * @ignore
             */
            contentEl: {
                view: 1
            }
        };

        return ContentBox;
    });