Doctrine\ODM\CouchDB\UnitOfWork::getDocumentIdentifier PHP Method

    public function getDocumentIdentifier($document)
    {
        $oid = \spl_object_hash($document);
        if (isset($this->documentIdentifiers[$oid])) {
            return $this->documentIdentifiers[$oid];
        } else {
            throw new CouchDBException("Document is not managed and has no identifier.");
        }
    }