public function addStructureNode(ChildStructureNode $l)
    {
        if ($this->collStructureNodes === null) {
            $this->initStructureNodes();
            $this->collStructureNodesPartial = true;
        }

        if (!$this->collStructureNodes->contains($l)) {
            $this->doAddStructureNode($l);
        }

        return $this;
    }