*
     * @param inputStream An input stream.
     * @param params A map of parameters.
     * @param postFilter A post filter.
     * @return An extracted data.
     */
    protected ExtractData getText(final InputStream inputStream, final Map<String, String> params,
            final BiConsumer<ExtractData, InputStream> postFilter) {
        if (inputStream == null) {
            throw new CrawlerSystemException("The inputstream is null.");