* @return the thumbnail file or null if not found
     */
    public File getThumbnailFile(final Map<String, Object> docMap) {
        final String thumbnailPath = getImageFilename(docMap);
        if (StringUtil.isNotBlank(thumbnailPath)) {
            final File file = new File(baseDir, thumbnailPath);
            if (file.isFile()) {
                return file;
            }
        }
        return null;
    }

            final Integer size, final SortBuilder<?>... sortBuilders) {
        return getList(clazz, builder -> {
            if (StringUtil.isNotBlank(sessionId)) {
                if (queryBuilder instanceof BoolQueryBuilder) {
                    ((BoolQueryBuilder) queryBuilder).filter(QueryBuilders.termQuery(SESSION_ID, sessionId));
                } else {