Batch Transform does not take any python code for input. It takes model name (model is created using Model class - from sagemaker.model import Model and CreateModelStep). Model class accepts an inference script (not mandatory but is one of the parameters) which just focuses on handling incoming API requests. Input data is an S3 location (directory) only. All the records, in files within this directory, are sent to model for inference and corresponding ".out" files are created in output directory. The content type like 'text/csv' defines the kind of files read for inference. These differences make batch transform step/job unique.