 default, all items will have a radio button (if <b>radio</b> is missing from the JSON data).</p>

            <p>When a radio is checked, first child from each level under the selected one will be checked by default. Also, the parents
                will be checked all the way up to the root item.<br>All others branches will be unchecked. This functionality will break once there is a missing radio button
                (with the default options set). In this way you can form radio button groups.</p>

   