private function addError(array & $errors, string $message, array $nodes)
	{
		$errors[] = ['text' => $message, 'nodes' => $nodes];

		$errorGraph = null;
		foreach ($nodes as $node) {
			if ($errorGraph === null) {
				$errorGraph = $node->getGraph();
			} else {
				$nodeGraph = $node->getGraph();
				if ($nodeGraph !== $errorGraph) {
					$errorGraph = $node->getRootGraph();
					break;
				}
			}
		}

		$errorNodeId = '_error_'.md5($message).'_'.count($errors);
		$errorNode = $errorGraph->createNode($errorNodeId, ['label' => $message, 'type' => 'error']);
		foreach ($nodes as $node) {
			$errorGraph->createEdge(null, $errorNode, $node, ['type' => 'error']);
		}
	}