public function get_course_overviewfiles() {
        global $CFG;
        if (empty($CFG->courseoverviewfileslimit)) {
            return array();
        }
        require_once($CFG->libdir. '/filestorage/file_storage.php');
        require_once($CFG->dirroot. '/course/lib.php');
        $fs = get_file_storage();
        $context = context_course::instance($this->id);
        $files = $fs->get_area_files($context->id, 'course', 'overviewfiles', false, 'filename', false);
        if (count($files)) {
            $overviewfilesoptions = course_overviewfiles_options($this->id);
            $acceptedtypes = $overviewfilesoptions['accepted_types'];
            if ($acceptedtypes !== '*') {
                // Filter only files with allowed extensions.
                require_once($CFG->libdir. '/filelib.php');
                foreach ($files as $key => $file) {
                    if (!file_extension_in_typegroup($file->get_filename(), $acceptedtypes)) {
                        unset($files[$key]);
                    }
                }
            }
            if (count($files) > $CFG->courseoverviewfileslimit) {
                // Return no more than $CFG->courseoverviewfileslimit files.
                $files = array_slice($files, 0, $CFG->courseoverviewfileslimit, true);
            }
        }
        return $files;
    }