Patch nest_asyncio in notebooks only

[dzhulgakov]

The logic to call nest_asyncio was added in 587f9ac presumably to make notebook interactions easier.

However, it's a bad practice to unconditionally call global python patches from library code.

It caused some issues with vLLM integration and was patched in #481

We ran into different issues when using Outlines in our codebase. The unittests started hanging on shutdown because of stray asyncio threads.

I propose to make the patch happen only when running inside IPython. According to https://stackoverflow.com/questions/15411967/how-can-i-check-if-code-is-executed-in-the-ipython-notebook it's an ok detention method for notebooks. Other proposed methods are too narrow and e.g. don't capture Colab.

However, even better fix might be to remove this patch all together and instead include it explicitly in the notebooks of choice. @rlouf - do you have more context on what was the original issue?

[rlouf]

Thank you for opening a PR! It was indeed to make interaction with notebooks easier.

What’s your use case?

[rlouf]

When is ValueError raised?

[dzhulgakov]

It was there from #481 . Presumably some vllm integration but I didn't run into it myself

[rlouf]

We can remove it

[dzhulgakov]

What’s your use case?

We're trying to use Outlines in some proprietary codebase (thank you for building it!). In one of the tests just importing outlines caused the test to hang at shutdown. The symptom is that threading.py _shutdown tries to join some threads. And there's a bunch of asyncio threads stuck in the process. I didn't debug it further, but the test uses asyncio and multiprocessing so it's kind of involved. Commenting out nest_asyncio or applying this PR solves the issue.

Btw, I verified that builtins.__IPYTHON__ trick works correctly when importing in colab.

[rlouf]

Thank you for contributing!