def METHOD_NAME(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
    """Upgrades stacks to have the new version number."""
    parser = configparser.ConfigParser(interpolation = None)
    parser.read_string(serialized)
    # Update version number.
    if "metadata" not in parser:
        parser["metadata"] = {}
    parser["metadata"]["setting_version"] = "10"
    if "containers" in parser:
        # With the ContainerTree refactor, UM2 with Olsson block got moved to a separate definition.
        if "6" in parser["containers"]:
            if parser["containers"]["6"] == "ultimaker2":
                if "metadata" in parser and "has_variants" in parser["metadata"] and parser["metadata"]["has_variants"] == "True":  # This is an Olsson block upgraded UM2!
                    parser["containers"]["6"] = "ultimaker2_olsson"
                    del parser["metadata"]["has_variants"]
            elif parser["containers"]["6"] == "ultimaker2_extended":
                if "metadata" in parser and "has_variants" in parser["metadata"] and parser["metadata"]["has_variants"] == "True":  # This is an Olsson block upgraded UM2E!
                    parser["containers"]["6"] = "ultimaker2_extended_olsson"
                    del parser["metadata"]["has_variants"]
        # We should only have 6 levels when we start.
        if "7" in parser["containers"]:
            return ([], [])
        # We added the intent container in Cura 4.4. This means that all other containers move one step down.
        parser["containers"]["7"] = parser["containers"]["6"]
        parser["containers"]["6"] = parser["containers"]["5"]
        parser["containers"]["5"] = parser["containers"]["4"]
        parser["containers"]["4"] = parser["containers"]["3"]
        parser["containers"]["3"] = parser["containers"]["2"]
        parser["containers"]["2"] = "empty_intent"
        # Update renamed containers
        for key, value in parser["containers"].items():
            if value in _renamed_container_id_map:
                parser["containers"][key] = _renamed_container_id_map[value]
    result = io.StringIO()
    parser.write(result)
    return [filename], [result.getvalue()]