Exist-DB counting and grouping

xquery version "3.0";
<nodes>
{
    let $nodes := //classCode
    for $nodo in $nodes
    let $count := count($nodo)
    group by $nomeNodo := $nodo/text()
    order by $nomeNodo
    return
        <nodo>
            <nodeId>
            {string($nomeNodo)}
            </nodeId>
            <counter>
            {string($count)}
            </counter>
        </nodo>
}
</nodes>