* @param fields The fields to extract from the document.
     * @param tagFieldNames The names of the fields that contain tags.
     * @param roleFieldName The name of the field that contains role information.
     * @param langFieldName The name of the field that contains language information.
     * @param readingConverter The converter to use for reading fields.
     * @param contentsReadingConverter The converter to use for reading content fields.