/**     * Check if a vertex exists     *     * This will call self::getVertex() internally and checks if there     * was an exception thrown which represents an 404 request.     *     * @throws Exception When any other error than a 404 occurs     *     * @param mixed $graph    - graph name as a string or instance of Graph     * @param mixed $vertexId - the vertex identifier     *     * @return boolean     */    public function hasVertex($graph, $vertexId)    {        try {            // will throw ServerException if entry could not be retrieved            $this->getVertex($graph, $vertexId);            return true;        } catch (ServerException $e) {            // we are expecting a 404 to return boolean false            if ($e->getCode() === 404) {                return false;            }            // just rethrow            throw $e;        }    }

     /**     * Get a single vertex from a graph     *     * This will throw if the vertex cannot be fetched from the server<br><br>     *     * @throws Exception     *     * @param mixed  $graph      - graph name as a string or instance of Graph     * @param mixed  $vertexId   - the vertex identifier     * @param array  $options    optional, an array of options:     *                           <p>     *                           <li><b>_includeInternals</b> - true to include the internal attributes. Defaults to false</li>     *                           <li><b>_ignoreHiddenAttributes</b> - true to show hidden attributes. Defaults to false</li>     *                           </p>     * @param string $collection - if one uses a graph with more than one vertex collection one must provide the collection     *                           to load the vertex.     *     * @return Document     * @since 1.2     */    public function getVertex($graph, $vertexId, array $options = [], $collection = null)