aws lambda parsing multipart form with python3

handler_fieldstorage.py

from cgi import FieldStorage
from io import BytesIO


def parse_into_field_storage(fp, ctype, clength):
    fs = FieldStorage(
        fp=fp,
        environ={'REQUEST_METHOD': 'POST'},
        headers={
            'content-type': ctype,
            'content-length': clength
        },
        keep_blank_values=True
    )
    form = {}
    files = {}
    for f in fs.list:
        if f.filename:
            files.setdefault(f.name, []).append(f)
        else:
            form.setdefault(f.name, []).append(f.value)
    return form, files
  
def handler(event, context):
    body_file = BytesIO(bytes(event["body"], "utf-8"))
    form, files = parse_into_field_storage(
        body_file,
        event['headers']['content_type'],
        body_file.getbuffer().nbytes
    )
    
    print(form)
    print(files)
    
    return {
        "statusCode": 200,
        "body": json.dumps({})
    }

handler_parse.py

from cgi import parse_header, parse_multipart
import json


def handler(event, context):
    content_type = event['headers'].get('Content-Type', '') or event['headers'].get('content-type', '')
    c_type, c_data = parse_header(content_type)
    c_data["boundary"] = bytes(c_data["boundary"], "utf-8")
    body_file = BytesIO(bytes(event["body"], "utf-8"))
    form_data = parse_multipart(body_file, c_data)
    
    print(form_data)
    
    return {
        "statusCode": 200,
        "body": json.dumps({})
    }

Seems like cgi is somehow corrupting the files when reading from multipart/form-data