lost grouping information

<window height="600px" width="600px">
    <listbox id="lb1">
        <listgroup label="Group 1"/>
        <listitem label="Item 1.1"/>
        <listitem label="Item 1.2"/>
        <listgroup label="Group 2"/>
        <listitem label="Item 2.1"/>
        <listitem label="Item 2.2"/>
    </listbox>
    <button label="Clone Listbox">
        <attribute name="onClick">
        Listbox lb2=lb1.clone();
        alert("Listbox 1 hasGroup => "+ lb1.hasGroup()+ " and Listbox 2 hasGroup=> "+ lb2.hasGroup());
        </attribute>
    </button>
    <grid id="grid1">
        <rows>
            <group><label value="Group 1"/></group>
            <row><label value="Row 1.1"/></row>
            <row><label value="Row 1.2"/></row>
            <group><label value="Group 2"/></group>
            <row><label value="Row 2.1"/></row>
            <row><label value="Row 2.2"/></row>
        </rows>
    </grid>
    <button label="Clone Grid">
        <attribute name="onClick">
        Grid grid2=grid1.clone();
        alert("Grid 1 rows hasGroup => "+ grid1.getRows().hasGroup()+ " and Grid 2 rows hasGroup=> "+ grid2.getRows().hasGroup());
        </attribute>
    </button>