not-implemented

<?php

// create big dummy document:
$dom = new \DOMDocument();
$rootNode = $dom->appendChild($dom->createElement('root'));
for ($i = 0; $i <= 100; $i++) {
    $level1Node = $rootNode->appendChild($dom->createElement('level1'));
    for ($j = 0; $j <= 100; $j++) {
        $level2Node = $level1Node->appendChild($dom->createElement('level2'));
        for ($k = 0; $k <= 10; $k++) {