How to retrieve the user story and build model changesets from Rally

I need to pull the changeset belongs to userstory along with build changesets.

// load the data
_loadData : function(loadUi) {
console.log('load data started');
Ext.create('Rally.data.wsapi.Store', {
    model : ['User Story','Build']
    autoLoad : true,
    listeners : {
        load : function(myStore, data, success) {
            return this._processChangesetData(myStore, data, loadUi);
        },
    scope : this
    },
    fetch : [ 'FormattedID', 'Name', 'ScheduleState','Changesets', 'Iteration', 'Release' ,'Number', 'Status','Uri',]
});
},