Add OpenAI JSON Mode

[rlouf]

No description provided.

[lhoestq]

Hi remi ! do you mean response_format={"type": "json_object"} ?

I was recently making a demo using [lotus-ai] https://github.com/guestrin-lab/lotus to process pandas DataFrames with a model on HF but it seems to require JSON mode in outlines.

I also noticed #707 which seems to imply that it could be possible to have a workaround for this feature but it's missing documentation

[rlouf]

Yes that's what I mean. We have experimental support for JSON mode in outlines. It's a bit hidden in the documentation: https://dottxt-ai.github.io/outlines/latest/reference/generation/cfg/