code: def expire_hit(self, hit_id):
          
          try:
              self.mturk.update_expiration_for_hit(HITId=hit_id, ExpireAt=0)
          except Exception as ex:
              raise MTurkServiceException(
                  "Failed to expire HIT {}: {}".format(hit_id, str(ex))
              )
          return True
docs: Expire a HIT, which will change its status to "Reviewable",
          allowing it to be deleted.