public function saveGraph(
        \EasyRdf_Graph $graph,
        $uri = '',
        $headers = []
    ) {
        // Serialze the rdf.
        $turtle = $graph->serialise('turtle');

        // Checksum it.
        $checksum_value = sha1($turtle);

        // Set headers.
        $headers['Content-Type'] = 'text/turtle';
        $headers['digest'] = 'sha1=' . $checksum_value;

        // Save it.
        return $this->saveResource($uri, $turtle, $headers);
    }