Using mojito-session-addon example

controller.server.js

/*jslint anon:true, sloppy:true, nomen:true*/
YUI.add('home', function(Y, NAME) {

    /**
     * The home module.
     *
     * @module home
     */

    /**
     * Constructor for the Controller class.
     *
     * @class Controller
     * @constructor
     */
    Y.namespace('mojito.controllers')[NAME] = {

        /**
         * Method corresponding to the 'index' action.
         *
         * @param ac {Object} The ActionContext that provides access
         *        to the Mojito API.
         */
        index : function(ac) {
            ac.session.set("test", "test123");
            Y.log(ac.session.get("test"));
            ac.models.get('homeModelFoo').getData(function(err, data) {
                if (err) {
                    ac.error(err);
                    return;
                }
                ac.assets.addCss('./index.css');
                ac.done({
                    status : 'Mojito is working.',
                    data : data
                });
            });

        }
    };

}, '0.0.1', {
    requires : ['mojito', 'mojito-assets-addon', 'mojito-models-addon', 'homeModelFoo', "mojito-session-addon"]
});

i just set a session with .set
Could you tell me how to clear the session