Bootstrap's $navbar

Hi,  The ZEN Mojo Widget reference at ../csp/sys/%ZEN.Mojo.WidgetReference.bootstrap33xHomepage.cls is a great reference for viewing the different components available with each helper plugin - and it also supplies snippets of JSON code to use in your layout definitions.

I'm having problems with the Bootstrap $navbar component however. This is layout definition, with a navbar and button contained within the bar.:

ClientMethod getLayout(key, criteria) [ Language = javascript ]
{
  var layout = {};
  switch(key) {
  case 'home' :
   // add layout objects to the children array
layout = {type:'$navbar',id:'navbar-collapse3',brand:'Brand',children:[
    {type:'$nav',cssClass:'navbar-nav',children:[ 

{type:'$button',cssClass:'navbar-btn',content:'Sign in'}   ]}

]}

return layout;

} 

However, I do not get a navbar, or the word "Brand" as expected, and there is no clever collapsing of any content into a vertical menu, when the viewport is reduced.

Is there something else I need to include in my layout to use $navbar ?

Thanks

Steve