Fix bug in openai_aip.py caused by Pydantic

[chzhyang]

Fix bug in chunk.json() caused by Pydantic
#341
#353

Enviroment

python3.9 and python3.10

Reproduce

Send request by client.py

import openai
if __name__ == "__main__":
    openai.api_base = "http://localhost:8000/v1"
    openai.api_key = "none"
    for chunk in openai.ChatCompletion.create(
        model="chatglm2-6b",
        messages=[
            {
                "role": "system",
                "content": "You are a helpful assistant."
            },
            {
                "role": "user",
                "content": "Hello!"
            }
        ],
        stream=True
    ):
        if hasattr(chunk.choices[0].delta, "content"):
            print(chunk.choices[0].delta.content, end="", flush=True)

$ python client.py 
Traceback (most recent call last):
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 710, in _error_catcher
    yield
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 1077, in read_chunked
    self._update_chunk_length()
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 1012, in _update_chunk_length
    raise InvalidChunkLength(self, line) from None
urllib3.exceptions.InvalidChunkLength: InvalidChunkLength(got length b'', 0 bytes read)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/requests/models.py", line 816, in generate
    yield from self.raw.stream(chunk_size, decode_content=True)
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 937, in stream
    yield from self.read_chunked(amt, decode_content=decode_content)
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 1106, in read_chunked
    self._original_response.close()
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/contextlib.py", line 137, in __exit__
    self.gen.throw(typ, value, traceback)
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/urllib3/response.py", line 727, in _error_catcher
    raise ProtocolError(f"Connection broken: {e!r}", e) from e
urllib3.exceptions.ProtocolError: ("Connection broken: InvalidChunkLength(got length b'', 0 bytes read)", InvalidChunkLength(got length b'', 0 bytes read))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/sdp/ChatGLM2-6B/client.py", line 5, in <module>
    for chunk in openai.ChatCompletion.create(
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/openai/api_resources/abstract/engine_api_resource.py", line 166, in <genexpr>
    return (
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/openai/api_requestor.py", line 692, in <genexpr>
    return (
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/openai/api_requestor.py", line 115, in parse_stream
    for line in rbody:
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/requests/models.py", line 865, in iter_lines
    for chunk in self.iter_content(
  File "/home/sdp/miniconda3/envs/chatglm/lib/python3.9/site-packages/requests/models.py", line 818, in generate
    raise ChunkedEncodingError(e)
requests.exceptions.ChunkedEncodingError: ("Connection broken: InvalidChunkLength(got length b'', 0 bytes read)", InvalidChunkLength(got length b'', 0 bytes read))

[laoshancun]

#415
maybe model_dump_json is better than json.dumps(chunk.model_dump()).