### Confirm this is an issue with the Python library and not an underlying OpenAI API - [X] This is an issue with the Python library ### Describe the bug When streaming from azure open ai API the delta of the choice is None. In the python open ai client v1.42.0 delta is type `ChoiceDelta` i.e. not `None`. ### To Reproduce Run this code in line with ```python completion = await self._client.chat.completions.create( model=self.deployment.name, messages=cast(list[ChatCompletionMessageParam], messages), stream=True, temperature=temperature, ) async for response_chunk in completion: ... ``` The types are: `response_chunk: ChatCompletionChunk` `response_chunk.choices: list[Choice]` `response_chunk.choices[0].delta: ChoiceDelta` The response from azure open ai API returns `delta=None`when stream ends Response example: ``` sh Choice(delta=None, finish_reason=None ...........) ``` ### Code snippets _No response_ ### OS linux, ubuntu 20.04 ### Python version 3.12.1 ### Library version openai v 1.42.0