make the loss context manager easier to extend

[winglian]

What does this PR do?

Using ExitStack makes it easier to extend the functionality of the context manager wrapping the model(inputs) call. This can make it easier to add other things like logging contexts, checkpointing contexts, etc down the road.

e.g.

class CustomTrainer(Trainer):
    def compute_loss_context_manager(self):
        ctx_stack = super(). compute_loss_context_manager()
        my_custom_ctx = CustomContext(...)
        ctx_stack.enter_context(my_custom_ctx)
        return ctx_stack

Fixes # (issue)

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• Did you write any new necessary tests?

Who can review?

@SunMarc @ArthurZucker
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[SunMarc]

Thanks !

[SunMarc]

nice ! maybe add in the doctstring that users can easily extend the context manager also !

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[ArthurZucker]

+1 on documenting and thanks!