public function addIndexEngineIndexVersion(ChildIndexEngineIndexVersion $l)
    {
        if ($this->collIndexEngineIndexVersions === null) {
            $this->initIndexEngineIndexVersions();
            $this->collIndexEngineIndexVersionsPartial = true;
        }

        if (!in_array($l, $this->collIndexEngineIndexVersions->getArrayCopy(), true)) { // only add it if the **same** object is not already associated
            $this->doAddIndexEngineIndexVersion($l);
        }

        return $this;
    }