Return the last week of the given year.
        This week with either have week-number 52 or 53.

        This will be the same as Week(year+1, 0), but will even work for
        year 9999 where this expression would overflow.

        The first week of a given year is simply Week(year, 1), so there
        is no dedicated classmethod for that.

def last_week_of_year(cls, year):
        """Return the last week of the given year.
        This week with either have week-number 52 or 53.

        This will be the same as Week(year+1, 0), but will even work for
        year 9999 where this expression would overflow.

        The first week of a given year is simply Week(year, 1), so there
        is no dedicated classmethod for that.
        """
        if year == cls.max.year:
            return cls.max
        return cls(year+1, 0)