code: def annual_heating_design_day_990(self):
          
          if bool(self._winter_des_day_dict) is True:
              return DesignDay.from_ashrae_dict_heating(
                  self._winter_des_day_dict, self.location, True,
                  self._stand_press_at_elev)
          else:
              return None
docs: A design day object representing the annual 99.0% heating design day.