def __new__(cls):
    """Validate the Meta class."""
    cls._meta = getattr(cls, 'Meta', type('Meta', (), {}))
    if 'class_list' not in cls._meta.__dict__:
        raise AttributeError("'class_list' is a required Meta class property")
    if 'navitems' not in cls._meta.__dict__:
        raise AttributeError("'navitems' is a required Meta class property")
    return super().__new__(cls)
