public function toDriverDocument()
    {
        $edge = new \triagens\ArangoDb\Edge;

        foreach ($this->_data as $key => $value) {
            $edge->set($key, $value);
        }

        if ($this->_id) {
            $edge->setInternalId($this->_id);
        }

        if ($this->_key) {
            $edge->setInternalKey($this->_key);
        }

        if ($this->_rev) {
            $edge->setRevision($this->_rev);
        }

        return $edge;
    }