public function retriveLayerObjects()
    {
        $classes = [];
        foreach ($this->engine->query('//dia:diagram/dia:layer') as $layer) {
            if ($layer->nodeName == 'dia:layer') {
                foreach ($layer->childNodes as $elementObject) {
                    if ($elementObject->nodeName == 'dia:object') {
                        foreach ($elementObject->childNodes as $childNodesAttributes) {
                            if ($childNodesAttributes->nodeName == 'dia:attribute' &&
                                    $childNodesAttributes->attributes->getNamedItem("name")->nodeValue == 'name'
                            ) {
                                $name = str_replace(['#'], [''], $childNodesAttributes->childNodes->item(1)->nodeValue);

                                $classes[$name] = $elementObject;
                            }
                        }
                    }
                }
            }
        }

        return $classes;
    }