'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.'

def extend_hit(self, hit_id, assignments_increment=None, expiration_increment=None):

    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)
