Computes holidays (non-working days) for a given year.
        Return a 2-item tuple, composed of the date and a label.

def holidays(self, year=None):
        """Computes holidays (non-working days) for a given year.
        Return a 2-item tuple, composed of the date and a label."""
        if not year:
            year = date.today().year

        if year in self._holidays:
            return self._holidays[year]

        # Here we process the holiday specific calendar
        temp_calendar = tuple(self.get_calendar_holidays(year))

        # it is sorted
        self._holidays[year] = sorted(temp_calendar)
        return self._holidays[year]