public static function define_decode_contents() {

        $prefix = 'qtype_'.self::qtype_name();

        $contents = array();

        $fields = array('correctfeedback', 'partiallycorrectfeedback', 'incorrectfeedback');
        $contents[] =
            new restore_decode_content($prefix, $fields, $prefix);

        return $contents;
    }