Error: Using Batch processing with a Pydantic models doesn't folllow under the main idea of batch processing #2091

import json

from typing import Any, List, Literal, Union
from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.utilities.batch import BatchProcessor, EventType, batch_processor
from aws_lambda_powertools.utilities.parser.models import SqsRecordModel
from aws_lambda_powertools.utilities.data_classes.sqs_event import SQSRecord
from aws_lambda_powertools.utilities.batch import (BatchProcessor,
                                                   EventType,
                                                   FailureResponse,
                                                   SuccessResponse,
                                                   batch_processor)

from aws_lambda_powertools.utilities.parser import BaseModel, validator


class Order(BaseModel):
    item: dict

class OrderSqsRecord(SqsRecordModel):
    body: Order

    # auto transform json string
    # so Pydantic can auto-initialize nested Order model
    @validator("body", pre=True)
    def transform_body_to_dict(cls, value: str):
        return json.loads(value)

processor = BatchProcessor(event_type=EventType.SQS, model=OrderSqsRecord)
tracer = Tracer()
logger = Logger()


@tracer.capture_method
def record_handler(record: OrderSqsRecord):
    return record.body.item

@tracer.capture_lambda_handler
def lambda_handler(event, context):
    batch = event["Records"]
    with processor(records=batch, handler=record_handler):
        processed_messages: List[Union[SuccessResponse, FailureResponse]] = processor.process()

    for message in processed_messages:
        status: Union[Literal["success"], Literal["fail"]] = message[0]
        result: Any = message[1]
        record: SQSRecord = message[2]

    logger.info(processor.response())
    return processor.response()


if __name__ == "__main__":
    event = {
        "Records": [
            {
            "messageId": "messageId-1",
            "receiptHandle": "AQEBwJnKyrHigUMZj6rYigCgxlaS3SLy0a...",
            "body": '{"item": 1}',
            "attributes": {
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1545082649183",
                "SenderId": "1",
                "ApproximateFirstReceiveTimestamp": "1545082649185"
            },
            "messageAttributes": {},
            "md5OfBody": "e4e68fb7bd0e697a0ae8f1bb342846b3",
            "eventSource": "aws:sqs",
            "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:my-queue",
            "awsRegion": "us-east-2"
            },
{
            "messageId": "messageId-2",
            "receiptHandle": "AQEBwJnKyrHigUMZj6rYigCgxlaS3SLy0a...",
            "body": 'Hi',
            "attributes": {
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1545082649183",
                "SenderId": "AIDAIENQZJOLO23YVJ4VO",
                "ApproximateFirstReceiveTimestamp": "1545082649185"
            },
            "messageAttributes": {},
            "md5OfBody": "e4e68fb7bd0e697a0ae8f1bb342846b3",
            "eventSource": "aws:sqs",
            "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:my-queue",
            "awsRegion": "us-east-2"
            }
        ]
    }
    lambda_handler(event,{})

Traceback (most recent call last):
  File "C:\Users\Crumpet\Desktop\AWS\powertools\model_test.py", line 90, in <module>
    lambda_handler(event,{})
  File "C:\Users\Crumpet\AppData\Local\Programs\Python39\lib\site-packages\aws_lambda_powertools\tracing\tracer.py", line 305, in decorate
    response = lambda_handler(event, context, **kwargs)
  File "C:\Users\Crumpet\Desktop\AWS\powertools\model_test.py", line 42, in lambda_handler
    processed_messages: List[Union[SuccessResponse, FailureResponse]] = processor.process()
  File "C:\Users\Crumpet\AppData\Local\Programs\Python39\lib\site-packages\aws_lambda_powertools\utilities\batch\base.py", line 97, in process
    return [self._process_record(record) for record in self.records]
  File "C:\Users\Crumpet\AppData\Local\Programs\Python39\lib\site-packages\aws_lambda_powertools\utilities\batch\base.py", line 97, in <listcomp>
    return [self._process_record(record) for record in self.records]
  File "C:\Users\Crumpet\AppData\Local\Programs\Python39\lib\site-packages\aws_lambda_powertools\utilities\batch\base.py", line 474, in _process_record
    data = self._to_batch_type(record=record, event_type=self.event_type, model=self.model)
  File "C:\Users\Crumpet\AppData\Local\Programs\Python39\lib\site-packages\aws_lambda_powertools\utilities\batch\base.py", line 347, in _to_batch_type
    return model.parse_obj(record)
  File "pydantic\main.py", line 526, in pydantic.main.BaseModel.parse_obj
  File "pydantic\main.py", line 341, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for OrderSqsRecord
body -> item
  value is not a valid dict (type=type_error.dict)