Common SetHITTypeNotification operation to set notification for a
        specified HIT type

def _set_notification(self, hit_type, transport, destination, event_types=None):
        """
        Common SetHITTypeNotification operation to set notification for a
        specified HIT type
        """
        assert type(hit_type) is str, "hit_type argument should be a string."
        
        params = {'HITTypeId': hit_type}
        
        # from the Developer Guide:
        # The 'Active' parameter is optional. If omitted, the active status of
        # the HIT type's notification specification is unchanged. All HIT types
        # begin with their notification specifications in the "inactive" status.
        notification_params = {'Destination': destination,
                               'Transport': transport,
                               'Version': boto.mturk.notification.NotificationMessage.NOTIFICATION_VERSION,
                               'Active': True,
                               }

        # add specific event types if required
        if event_types:
            self.build_list_params(notification_params, event_types, 'EventType')
        
        # Set up dict of 'Notification.1.Transport' etc. values
        notification_rest_params = {}
        num = 1
        for key in notification_params:
            notification_rest_params['Notification.%d.%s' % (num, key)] = notification_params[key]
        
        # Update main params dict
        params.update(notification_rest_params)
        
        # Execute operation
        return self._process_request('SetHITTypeNotification', params)