def backoff_time(self, response: requests.Response) -> Optional[float]:
    if (response.status_code == 429):
        return int(response.headers.get('Retry-After', 0))
def backoff_time(self, response: requests.Response) -> Optional[float]:
    if (response.status_code == 429):
        return int(response.headers.get('Retry-After', 0))