Feature Request: Improved Support/Documentation for PipelineModel

[jfelectron]

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While an example includes use of PipelineModel: https://github.com/aws/aws-step-functions-data-science-sdk-python/blob/main/src/stepfunctions/template/pipeline/inference.py#L128

This is a no-op: https://github.com/aws/aws-step-functions-data-science-sdk-python/blob/main/src/stepfunctions/template/pipeline/inference.py#L142

Setting the parameters property results in no changes to the CreateModel API call. Instead, this method should be called: https://github.com/aws/aws-step-functions-data-science-sdk-python/blob/master/src/stepfunctions/steps/states.py#L201

which performs the desired update: self.fields[Field.Parameters.value] = params

Overall, while the example should likely be updated and documentation provided on use of PipelineModel, this method of parameter updating feels like a workaround. Ideally, ModelStep could take PipelineModel as input.