ENH: Add "[DONE]" to the end of stream generation for better openai SDK compatibility

[ZhangTianrong]

The official API from OpenAI always send a "[DONE]" before it terminates the stream. Although redundant, some clients like ChatGPT.好友 rely on it instead of a non-empty finish_reason to determine the the end of the stream. So, it might be beneficial to abide by this convension.

fixes #998

[ZhangTianrong]

test_client.py requires all chunks in the stream generation to be a valid json object, but "[DONE]" is supposed to be a special case. It's worth modifying the test to handle the last chunk specifically.

[qinxuye]

test_client.py requires all chunks in the stream generation to be a valid json object, but "[DONE]" is supposed to be a special case. It's worth modifying the test to handle the last chunk specifically.

I think you can strip the [DONE] and make the tests passed.

[ZhangTianrong]

It seems that the assert in test_client.py is not working. In assert "content" or "role" in chunk["choices"][0]["delta"], since comparation operators like in takes precedence over logical operators like or and "content" is a non empty, the statement always evaluates to True.