Urllib error when trying to use list inside a form-data

Describe the bug

I have an API that accepts a JSON list inside form-data, so the request is expected to look like this:

input=[{...}, {...}]

However, when I pass the list to the generated client, the request fails with the following error.

Could you please take a look and let me know what might be going wrong here?

from openapi_client import ApiClient, Configuration, DefaultApi, SubmitPostRequestInput, SubmitItem

config = Configuration()
config.host = "https://api.example.com"
api_client = ApiClient(configuration=config)
api_instance = DefaultApi(api_client)


request_input = SubmitPostRequestInput(
    [
        SubmitItem(flag1=True, flag2=False),
        SubmitItem(flag1=False, flag2=True)
    ]
)
api_instance.submit_post(input=request_input, inlcude_ses=True)

With the generated client and the code above I am getting the following error

File c:\Users\1592\AppData\Local\Programs\Python\Python311\Lib\site-packages\urllib3\_request_methods.py:264, in RequestMethods.request_encode_body(self, method, url, fields, headers, encode_multipart, multipart_boundary, **urlopen_kw)
    259     raise TypeError(
    260         "request got values for both 'fields' and 'body', can only specify one."
    261     )
    263 if encode_multipart:
--> [264](file:///C:/Users/1592/AppData/Local/Programs/Python/Python311/Lib/site-packages/urllib3/_request_methods.py:264)     body, content_type = encode_multipart_formdata(
    265         fields, boundary=multipart_boundary
    266     )
    267 else:
    268     body, content_type = (
    269         urlencode(fields),  # type: ignore[arg-type]
    270         "application/x-www-form-urlencoded",
    271     )

File c:\Users\1592\AppData\Local\Programs\Python\Python311\Lib\site-packages\urllib3\filepost.py:[81](file:///C:/Users/1592/AppData/Local/Programs/Python/Python311/Lib/site-packages/urllib3/filepost.py:81), in encode_multipart_formdata(fields, boundary)
     79         writer(body).write(data)
     80     else:
---> 81         body.write(data)
     83     body.write(b"\r\n")
     85 body.write(f"--{boundary}--\r\n".encode("latin-1"))

TypeError: a bytes-like object is required, not 'list'

Please use the below spec file and above sample snippet to reproduce the issue

OpenAPI Spec File

openapi: 3.0.3
info:
  title: Simple Form Data API
  version: 1.0.0

paths:
  /submit:
    post:
      summary: Submit form data with flags
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                input:
                  oneOf:
                    - $ref: '#/components/schemas/SubmitItem'
                    - type: array
                      items:
                        $ref: '#/components/schemas/SubmitItem'
                inlcude_ses:
                  type: boolean
      responses:
        '200':
          description: Successful submission

components:
  schemas:
    SubmitItem:
      type: object
      properties:
        flag1:
          type: boolean
        flag2:
          type: boolean

Desktop (please complete the following information):

• OS: windows
• Python Version: 3.11
• openapi-generator version - 7.20.0-SNAPSHOT (Docker)

Tái hiện lỗi bằng đặc tả OpenAPI và mẫu được cung cấp, sử dụng ApiClient và DefaultApi.submit_post, tập trung vào SubmitPostRequestInput và việc xử lý multipart/form-data. Theo dõi quá trình tuần tự hóa request được tạo cho đến urllib3, sau đó xác minh rằng một danh sách các giá trị SubmitItem được chấp nhận mà không gặp bytes-like-object TypeError.