Setup Pre-Commit

[ParagEkbote]

When I was working on #303, the pre-commit was not setup. This PR does the same. I have taken reference from this repo: https://github.com/optuna/optuna/blob/master/.pre-commit-config.yaml. Please let me know if any improvements are needed and I will make the necessary changes.

cc: @c-bata

[HideakiImamura]

@gen740 Could you review this PR?

[ParagEkbote]

Could you please review the changes?

cc: @gen740

[github-actions]

This pull request has not seen any recent activity.

[ParagEkbote]

Not stale

[ParagEkbote]

Could you please review the changes?

cc: @gen740

[gen740]

I’m so sorry for my late reply, and thank you very much for your pull request!
(I was on a business trip…)

I ran the pre-commit hook on your branch, and the following error occurred:

> pre-commit run --all-files
black....................................................................Passed
flake8...................................................................Passed
isort....................................................................Passed
mypy.....................................................................Failed
- hook id: mypy
- exit code: 2

pytorch/pytorch_simple.py: error: Duplicate module named "pytorch_simple" (also at "multi_objective/pytorch_simple.py")
pytorch/pytorch_simple.py: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#mapping-file-paths-to-modules for more info
pytorch/pytorch_simple.py: note: Common resolutions include: a) using `--exclude` to avoid checking one of them, b) adding `__init__.py` somewhere, c) using `--explicit-package-bases` or adjusting MYPYPATH
Found 1 error in 1 file (errors prevented further checking)

Does this also happen on your machine?
I guess the pre-commit hook should run the same checks as defined in .github/workflows/checks.yml
Currently, that doesn’t seem to be the case, which means mypy checks aren’t guaranteed to run.

Also, it would be really helpful for beginners if you added instructions to CONTRIBUTING.md, just like Optuna does.
https://github.com/optuna/optuna/blob/022f97dbcb9be635ba2987662a33f684ad9811f0/CONTRIBUTING.md?plain=1#L81-L90

[ParagEkbote]

Since this repo doesn't include checks for mypy as seen in the config file here, I've removed it from the pre-commit file and now all the checks are passing.

Could you please review?

cc: @gen740

[gen740]

LGTM!