public function initialize()
    {
        if ($this->versionStorage->hasVersioningNode()) {
            throw new MigratorException('This repository has already been initialized. Will not re-initialize.');
        }

        foreach (array_keys($this->versionCollection->getAllVersions()) as $timestamp) {
            $this->versionStorage->add($timestamp);
        }

        $this->session->save();
    }