docs: def saturdays_of_weekends(self) -> Set[datetime.date]:
          """
          Returns the dates of all Saturdays that are part of weekends that this
          interval covers (each Saturday representing a unique identifier for
          that weekend). The Saturday itself isn't necessarily the part of the
          weekend that the interval covers!
          """
          startdate = self.start.date()
          enddate = self.end.date()
          ndays = (enddate - startdate).days + 1
          saturdays = set()
          for i in range(ndays):
              date = startdate + datetime.timedelta(days=i)
              if is_saturday(date):
                  saturdays.add(date)
              elif is_sunday(date):
                  saturdays.add(date - datetime.timedelta(days=1))
          return saturdays