how to log error/messages in while running a sagemaker batch transform job?

i'm using a hugging face model and a container to create a batch transform job in sagemaker. i have a custom inference code and in the output_fn function i'm returning json_dumps(prediction). I'm using print(prediction) to see, if i can see it in the cloudwatch logs to find out type and what prediction is. how can log these messages . Also, the inference output i get is in the form below., i'm not sure why is it not a json object in each line instead it has square brackets. I want to use the filter to match the input and output in the batch job. I'm not sure how the output should look like , because i'm trying to associate input with output by using dataprocessing config as below. but i get an error. the documenation has example of csv not json. what should the output look like so that i can associate the input with output when they both are in json format.

  "DataProcessing": {
        "JoinSource": "Input"
    },

[ output text 1 ]
[output text 2 ]

# Serialize the prediction result into the desired response content type
def output_fn(prediction, accept=JSON_CONTENT_TYPE):
    logger.info("Serializing the generated output.")
    if accept == JSON_CONTENT_TYPE:
        output = json.dumps(prediction)
        return output, accept
    raise Exception("Requested unsupported ContentType in Accept: {}".format(accept))