public function generateVCF(array $nodes)
    {
        $output = '';

        foreach ($nodes as $node) {
            if (!isset($node[200]['{'.Plugin::NS_CARDDAV.'}address-data'])) {
                continue;
            }
            $nodeData = $node[200]['{'.Plugin::NS_CARDDAV.'}address-data'];

            // Parsing this node so VObject can clean up the output.
            $vcard = VObject\Reader::read($nodeData);
            $output .= $vcard->serialize();

            // Destroy circular references to PHP will GC the object.
            $vcard->destroy();
        }

        return $output;
    }