public function exportIndex(
        Repository $repository,
        string $format
    ): string {
        $allItems = [];
        $iteration = 0;
        while (true) {
            $items = $repository
                ->query(Query::create('', $iteration, 10000))
                ->getItems();

            if (empty($items)) {
                break;
            }

            $allItems = array_merge(
                $allItems,
                $items
            );

            ++$iteration;
        }

        return $this
            ->exporterCollection
            ->getExporterByName($format)
            ->itemsToFormat($allItems);
    }