public static function get_user_dates_parameters() {
        return new external_function_parameters(
            [
                'contextid' => new external_value(
                    PARAM_INT,
                    'Context ID. Either use this value, or level and instanceid.',
                    VALUE_DEFAULT,
                    0
                ),
                'contextlevel' => new external_value(
                    PARAM_ALPHA,
                    'Context level. To be used with instanceid.',
                    VALUE_DEFAULT,
                    ''
                ),
                'instanceid' => new external_value(
                    PARAM_INT,
                    'Context instance ID. To be used with level',
                    VALUE_DEFAULT,
                    0
                ),
                'timestamps' => new external_multiple_structure (
                    new external_single_structure (
                        [
                            'timestamp' => new external_value(PARAM_INT, 'unix timestamp'),
                            'format' => new external_value(PARAM_TEXT, 'format string'),
                        ]
                    )
                )
            ]
        );
    }