Problem with CheckpointConfig s3uri in Tensorflow estimator

Values from estimator not passing to the step function definition (JSON). Had to manually set it in json by editing the step function from console to make the training job work.

` "CheckpointConfig": {
"S3Uri": "s3://bucket_name/location/for/checkpoint/"
},`
S3Uri is taken from `checkpoint_s3_uri` right? but in my case this is not working. `CheckpointConfig `dictionary is not generated.

Thank you for taking a look at it.

首先跟踪 TensorFlow estimator 的 checkpoint_s3_uri，直到生成的 Step Functions JSON，重点检查 CheckpointConfig 及其 S3Uri 字段。完成的标准是 estimator 生成的定义包含预期的 CheckpointConfig 和 S3Uri，从而使训练作业无需在控制台中手动编辑即可运行。

由索引模型根据 Issue 内容生成。