[Code] add pytorch-lightning compatibility for 1.7.x

[JiahaoYao]

update for pytorch lightning 1.7.

[awaelchli]

A small note here: We just merged Lightning-AI/pytorch-lightning#14319, which will go into the next 1.7.x release. It introduces the environment variable PL_DISABLE_FORK, which should be set by frameworks that don't support forking. So I suggest that we set PL_DISABLE_FORK=1 in Ray-Lightning. What do you think?

More context:
Lightning-AI/pytorch-lightning#14292
ray-project/ray#27493

[JiahaoYao]

Thanks for your @awaelchli prompt response. I will take a look!

[aga-relation]

Any updates on when a release supporting torch-lightning 1.7.x might be expected? :)

[geoffrey-g-delhomme]

Any updates?

[lcaquot94]

Is there an availability date planned for torch-lightning 1.7 or 1.8 ?
Thank you ?

[amogkam]

Hi all, there is a WIP PR: #222, but unfortunately I don't have the bandwidth any time soon to pick it up.

Any community contributions here are welcome!