public static function get_wikis_by_courses_returns() {

        return new external_single_structure(
            array(
                'wikis' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'id' => new external_value(PARAM_INT, 'Wiki ID.'),
                            'coursemodule' => new external_value(PARAM_INT, 'Course module ID.'),
                            'course' => new external_value(PARAM_INT, 'Course ID.'),
                            'name' => new external_value(PARAM_RAW, 'Wiki name.'),
                            'intro' => new external_value(PARAM_RAW, 'Wiki intro.', VALUE_OPTIONAL),
                            'introformat' => new external_format_value('Wiki intro format.', VALUE_OPTIONAL),
                            'introfiles' => new external_files('Files in the introduction text', VALUE_OPTIONAL),
                            'timecreated' => new external_value(PARAM_INT, 'Time of creation.', VALUE_OPTIONAL),
                            'timemodified' => new external_value(PARAM_INT, 'Time of last modification.', VALUE_OPTIONAL),
                            'firstpagetitle' => new external_value(PARAM_RAW, 'First page title.', VALUE_OPTIONAL),
                            'wikimode' => new external_value(PARAM_TEXT, 'Wiki mode (individual, collaborative).', VALUE_OPTIONAL),
                            'defaultformat' => new external_value(PARAM_TEXT, 'Wiki\'s default format (html, creole, nwiki).',
                                                                            VALUE_OPTIONAL),
                            'forceformat' => new external_value(PARAM_INT, '1 if format is forced, 0 otherwise.',
                                                                            VALUE_OPTIONAL),
                            'editbegin' => new external_value(PARAM_INT, 'Edit begin.', VALUE_OPTIONAL),
                            'editend' => new external_value(PARAM_INT, 'Edit end.', VALUE_OPTIONAL),
                            'section' => new external_value(PARAM_INT, 'Course section ID.', VALUE_OPTIONAL),
                            'visible' => new external_value(PARAM_INT, '1 if visible, 0 otherwise.', VALUE_OPTIONAL),
                            'groupmode' => new external_value(PARAM_INT, 'Group mode.', VALUE_OPTIONAL),
                            'groupingid' => new external_value(PARAM_INT, 'Group ID.', VALUE_OPTIONAL),
                            'cancreatepages' => new external_value(PARAM_BOOL, 'True if user can create pages.'),
                        ), 'Wikis'
                    )
                ),
                'warnings' => new external_warnings(),
            )
        );
    }