ModelTrainer supports SDK Defaults Config but is not in the Documentations

[benieric]

What did you find confusing? Please describe.

• https://sagemaker.readthedocs.io/en/stable/overview.html#configuring-and-using-defaults-with-the-sagemaker-python-sdk
• ModelTrainer has support but not in the readthedocs - https://github.com/aws/sagemaker-python-sdk/blob/master/src/sagemaker/modules/train/model_trainer.py#L278

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