public function display_grade($grade, $editable, $userid, $modified) {
        if ($this->is_downloading()) {
            if ($this->assignment->get_instance()->grade >= 0) {
                if ($grade == -1 || $grade === null) {
                    return '';
                }
                $gradeitem = $this->assignment->get_grade_item();
                return format_float($grade, $gradeitem->get_decimals());
            } else {
                // This is a custom scale.
                $scale = $this->assignment->display_grade($grade, false);
                if ($scale == '-') {
                    $scale = '';
                }
                return $scale;
            }
        }
        return $this->assignment->display_grade($grade, $editable, $userid, $modified);
    }