def incrementing_sleep(self, previous_attempt_number, delay_since_first_attempt_ms):
        """
        Sleep an incremental amount of time after each attempt, starting at
        wait_incrementing_start and incrementing by wait_incrementing_increment
        """
        result = self._wait_incrementing_start + (self._wait_incrementing_increment * (previous_attempt_number - 1))
        if result > self._wait_incrementing_max:
            result = self._wait_incrementing_max
        if result < 0:
            result = 0
        return result

        Sleep an incremental amount of time after each attempt, starting at
        wait_incrementing_start and incrementing by wait_incrementing_increment
        
retrying.py