function isExponentialRetryResponse(response) {
    return Boolean(response &&
        response.status !== undefined &&
        (response.status >= 500 || response.status === 408) &&
        response.status !== 501 &&
        response.status !== 505);
}
The header that comes back from services representing
the amount of time (minimum) to wait to retry (in seconds or timestamp after which we can retry).