Neos\Media\Domain\Repository\AssetRepository::addAssetCollectionToQueryConstraints PHP Method

    protected function addAssetCollectionToQueryConstraints(Query $query, AssetCollection $assetCollection = null)
    {
        if ($assetCollection === null) {
            return;
        }
        $constraints = $query->getConstraint();
        $query->matching($query->logicalAnd($constraints, $query->contains('assetCollections', $assetCollection)));
    }