error for public ecr image

**Link to the notebook**
[Add the link to the notebook.](https://github.com/aws/amazon-sagemaker-examples/blob/main/sagemaker_batch_transform/pytorch_mnist_batch_transform/pytorch-mnist-batch-transform.ipynb)

**Describe the bug**
I refer to the above notebook to test in my sagemaker notebook instance. But got error:
UnexpectedStatusException: Error for Transform job pytorch-training-2022-04-26-03-49-17-847: Failed. Reason: ClientError: API error (404): manifest for 727897471807.dkr.ecr.cn-north-1.amazonaws.com.cn/pytorch-inference:1.8.0-cpu-py3 not found: manifest unknown: Requested image not found

I think the ecr image :727897471807.dkr.ecr.cn-north-1.amazonaws.com.cn/pytorch-inference:1.8.0-cpu-py3 is built-in image.
So, anything is changed?
In other word, only for the cn-north-1 region this is not applicable

Open sagemaker_batch_transform/pytorch_mnist_batch_transform/pytorch-mnist-batch-transform.ipynb and reproduce the batch transform in cn-north-1. Inspect the referenced pytorch-inference:1.8.0-cpu-py3 image and the resulting manifest error. Done means establishing whether this notebook applies in cn-north-1 and recording the confirmed behavior or required guidance.

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