'Issues a payment of money from your account to a Worker.  To
be eligible for a bonus, the Worker must have submitted
results for one of your HITs, and have had those results
approved or rejected. This payment happens separately from the
reward you pay to the Worker when you approve the Worker\'s
assignment.  The Bonus must be passed in as an instance of the
Price object.'

def grant_bonus(self, worker_id, assignment_id, bonus_price, reason):

    params = bonus_price.get_as_params('BonusAmount', 1)
    params['WorkerId'] = worker_id
    params['AssignmentId'] = assignment_id
    params['Reason'] = reason
    return self._process_request('GrantBonus', params)
