Apply filter on store

How to apply filter on Extjs store of a combobox

HTML

<link rel="stylesheet" href="http://extjs.cachefly.net/ext-4.0.2a/resources/css/ext-all.css">
Check the below link for detail explanation of this fiddle:
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<a href='http://atechiediary.blogspot.com/2013/06/extjs-how-to-filter-data-of-store-in.html'> Detail Blog entry </a>

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JavaScript

// The data store containing the list of cars
var cars = Ext.create('Ext.data.Store', {
    autoLoad: true,
    fields: ['key', 'name'],
    data: [{
        "key": "Benz",
            "name": "Mercedes-Benz"
    }, {
        "key": "Audi",
            "name": "Audi"
    }, {
        "key": "Ferrari",
            "name": "Ferrari"
    }, {
        "key": "Prius",
            "name": "Prius"
    }, {
        "key": "Lamborghini",
            "name": "Lamborghini"
    }, {
        "key": "BMW",
            "name": "BMW"
    }]
});

Ext.create('Ext.toolbar.Toolbar', {
    renderTo: document.body,
    items: [{
        xtype: 'combobox',
        fieldLabel: 'Choose Car',
        labelWidth: 70,
        store: cars,
        queryMode: 'local',
        displayField: 'name',
        valueField: 'key'
    }, {
        xtype: 'fieldcontainer',
        fieldLabel: 'Filter',
        defaultType: 'radiofield',
        labelWidth: 40,
        layout: 'hbox',
        items: [{
            boxLabel: 'Benz',
            name: 'size',
            id: 'radio1',
            listeners: {
                change: function (radio1, newvalue, oldvalue) {
                    //alert('radio1 - ' + newvalue + ' ::: ' + oldvalue);
                    if (newvalue) {
                        cars.clearFilter();
                        cars.filter('key', 'Benz');
                    }
                }
            }
        }, {
            boxLabel: 'BMW',
            name: 'size',
            id: 'radio2',
            listeners: {
                change: function (radio2, newvalue, oldvalue) {
                    //alert('radio2 - ' + newvalue + ' ::: ' + oldvalue);
                    if (newvalue) {
                        cars.clearFilter();
                        cars.filter('key', 'BMW');
                    }
                }
            }
        }, {
            boxLabel: 'Both',
            name: 'size',
            id: 'radio3',
            listeners: {
                change:...