public static function get_content_pages_viewed_returns() {
        return new external_single_structure(
            array(
                'pages' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'id' => new external_value(PARAM_INT, 'The attempt id.'),
                            'lessonid' => new external_value(PARAM_INT, 'The lesson id.'),
                            'pageid' => new external_value(PARAM_INT, 'The page id.'),
                            'userid' => new external_value(PARAM_INT, 'The user who viewed the page.'),
                            'retry' => new external_value(PARAM_INT, 'The lesson attempt number.'),
                            'flag' => new external_value(PARAM_INT, '1 if the next page was calculated randomly.'),
                            'timeseen' => new external_value(PARAM_INT, 'The time the page was seen.'),
                            'nextpageid' => new external_value(PARAM_INT, 'The next page chosen id.'),
                        ),
                        'The content pages viewed.'
                    )
                ),
                'warnings' => new external_warnings(),
            )
        );
    }