docs: private IpcAttempt extractAttempt(SdkHttpRequest request) {
      int attempt = 0;
      List<String> vs = request.headers().get("amz-sdk-retry");
      if (vs != null) {
        for (String v : vs) {
          // Format is: {requestCount - 1}/{lastBackoffDelay}/{availableRetryCapacity}
          // See internal RetryHandler for more details.
          int pos = v.indexOf('/');
          if (pos > 0) {
            try {
              attempt = Integer.parseInt(v.substring(0, pos)) + 1;
            } catch (NumberFormatException e) {
              // If we cannot parse it, then attempt is unknown
              attempt = 0;
            }
          }
        }
      }
      return IpcAttempt.forAttemptNumber(attempt);
    }