code: def extend_hit(self, hit_id, assignments_increment=None, expiration_increment=None):
          
          # must provide assignment *or* expiration increment
          if (assignments_increment is None and expiration_increment is None) or \
             (assignments_increment is not None and expiration_increment is not None):
              raise ValueError("Must specify either assignments_increment or expiration_increment, but not both")
  
          params = {'HITId' : hit_id,}
          if assignments_increment:
              params['MaxAssignmentsIncrement'] = assignments_increment
          if expiration_increment:
              params['ExpirationIncrementInSeconds'] = expiration_increment
  
          return self._process_request('ExtendHIT', params)
docs: Increase the maximum number of assignments, or extend the
          expiration date, of an existing HIT.
          
          NOTE: If a HIT has a status of Reviewable and the HIT is
          extended to make it Available, the HIT will not be returned by
          GetReviewableHITs, and its submitted assignments will not be
          returned by GetAssignmentsForHIT, until the HIT is Reviewable
          again.  Assignment auto-approval will still happen on its
          original schedule, even if the HIT has been extended. Be sure
          to retrieve and approve (or reject) submitted assignments
          before extending the HIT, if so desired.