Hes Song

In the [official document](https://docs.aws.amazon.com/sagemaker/latest/APIReference/API_AthenaDatasetDefinition.html), there are several parameters that are required. However, in this [SDK](https://github.com/aws/sagemaker-python-sdk/blob/b4f05b86a90f4ae202ad7f9b048922ab490731fe/src/sagemaker/dataset_definition/inputs.py#L75), default values for those are set as 'None' Is there any reason not for marking...