kendoAutoComplete clear

HTML

<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.2.710/styles/kendo.common.min.css">
<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.2.710/styles/kendo.default.min.css">
<script src="http://cdn.kendostatic.com/2012.2.913/js/kendo.all.min.js"></script>
<div id="content">

<input id="getPersonListByFirstName" data-role="autocomplete" data-text-field="Description"
                    data-bind="source: datas, value: nom, events: { select: getPersonListByFirstNameSelect }" />
    <br/><span data-bind="text: nom"></span><br/><span data-bind="text: prenom"></span>
    
</div>

<input id="reset" type="button" value="initialize">

JavaScript

var listPerson = [{
    "Id": 13896,
    "FirstName": "Mathieu",
    "LastName": "Beland",
    "Description": "Mathieu Beland"},
{
    "Id": 13897,
    "FirstName": "Michel",
    "LastName": "Brisebois",
    "Description": "Michel Brisebois"},
{
    "Id": 13898,
    "FirstName": "Tristan",
    "LastName": "Dube",
    "Description": "Tristan Dube"},
{
    "Id": 13899,
    "FirstName": "ROBERT M.",
    "LastName": "GRANATSTEIN",
    "Description": "ROBERT M. GRANATSTEIN"},
{
    "Id": 13900,
    "FirstName": "JEFFREY R.",
    "LastName": "LLOYD",
    "Description": "JEFFREY R. LLOYD"},
{
    "Id": 13901,
    "FirstName": "GIBSON",
    "LastName": "BROCK",
    "Description": "GIBSON BROCK"},
{
    "Id": 13902,
    "FirstName": "ROBERT",
    "LastName": "GRANATSTEIN",
    "Description": "ROBERT GRANATSTEIN"},
{
    "Id": 13903,
    "FirstName": "CASSELS & GRAYDON LLP",
    "LastName": "BLAKE",
    "Description": "CASSELS & GRAYDON LLP BLAKE"}];

var viewModel = kendo.observable({
    datas: listPerson,
    nom: null,
    prenom: null,
    getPersonListByFirstNameSelect: function myfunction(eventArgs) {
        eventArgs.preventDefault();
        var autocomplete = $("#getPersonListByFirstName").data("kendoAutoComplete");
        var dataItem = autocomplete.dataItem(eventArgs.item.index());
        this.set("nom", dataItem.FirstName);
        this.set("prenom", dataItem.LastName);
    }
});

kendo.bind($('#content'), viewModel);

$("#reset").click(function() {
    viewModel.set("nom", "Brisebois");
    viewModel.set("prenom", "Michel");
});