code: def _start_of_week(self):
          
          dt = self
  
          if self.day_of_week != pendulum._WEEK_STARTS_AT:
              dt = self.previous(pendulum._WEEK_STARTS_AT)
  
          return dt.start_of("day")
docs: Reset the date to the first day of the week
          and the time to 00:00:00.
  
          :rtype: DateTime