Continue getting "string argument should contain only ASCII characters" on aws lambda with api gateway

I want to create simple python aws lambda function which works with pdf files.

I followed the instruction from aws docs and created docker image, pushed it to AWS ECR and created lambda basing on it.

I want to send file in POST request body with content type application/pdf.Then i added api gateway in front of it and added media type application/pdf.

But i still get this error. Does anybody knows any solutions?

Here is my lambda code

import jsonimport base64import pdfplumberimport ioimport loggingdef lambda_handler(event, context):   try:       pdf_data = base64.b64decode(event["body"])       pdf_file = io.BytesIO(pdf_data)       with pdfplumber.open(pdf_file) as pdf:           tables = [               page.extract_tables(                   table_settings={"vertical_strategy": "lines_strict","horizontal_strategy": "lines_strict",                   }               )               for page in pdf.pages           ]       return {"statusCode": 200,"body": json.dumps(               {"message": "Tables extracted successfully", "tables": tables}           ),       }   except Exception as e:       return {"statusCode": 500, "body": json.dumps({"error": str(e)})}

And here is my dockerfile

FROM public.ecr.aws/lambda/python:3.9COPY requirements.txt ${LAMBDA_TASK_ROOT}RUN pip install -r requirements.txtCOPY src/* ${LAMBDA_TASK_ROOT}CMD ["main.lambda_handler"]