public function getHasManyDbValue(RelationshipMetadata $relMeta, array $models = null)
    {
        if (null === $models || true === $relMeta->isInverse) {
            return null;
        }
        $references = [];
        foreach ($models as $model) {
            $references[] = $this->createReference($relMeta, $model);
        }
        return empty($references) ? null : $references;
    }