*
     * @param builder a {@link Consumer} that accepts an {@link XPathFactory} and configures it.
     * @return a configured instance of {@link XPath}.
     * @throws CrawlerSystemException if an error occurs while creating the {@link XPath} instance.
     */
    public XPath createXPath(final Consumer<XPathFactory> builder) {
        try {

     * @param consumer The callback.
     * @return The promise.
     */
    public Promise then(final Consumer<RESPONSE> consumer) {
        return promise.then(consumer);
    }

    /**
     * Registers a callback to be executed when the computation fails.
     * @param consumer The callback.
     * @return The promise.
     */