def __init__(self) -> None:
        super().__init__()

        # Listen to a Signal that indicates a change in the list of printers, just if the user has enabled the
        # "check for updates" option
        Application.getInstance().getPreferences().addPreference("info/automatic_update_check", True)
        if Application.getInstance().getPreferences().getValue("info/automatic_update_check"):
            ContainerRegistry.getInstance().containerAdded.connect(self._onContainerAdded)

        self._check_job = None
        self._checked_printer_names = set()  # type: Set[str]