[CI] Fix: flake8 rule B109: Using the functools.lru_cache and functools.cache decorators on methods can lead to memory leaks

[win5923]

Why are these changes needed?

While running the pre-commit hook of flake8, the following error occurs if Python version is 3.12. It's because the version of flake8 is too old.

version:

• python: 3.12.7
• flake8: 7.1.1
• flake8-bugbear: 24.8.19

Related issue number

Closes #48066

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[win5923]

@MortalHappiness PTAL

[MortalHappiness]

I wonder if the functools.cache here has no effect at all. As far as I know, functools.cache only caches function arguments, but this method has no arguments except for self.

Maybe the original author intended to use functools.cached_property, but I am not sure.

cc @rynewang

[rynewang]

@bveeramani can you take a look at this issue and see if we want to change this cache?

[MortalHappiness]

@bveeramani Hi why is this PR merged? I thought you intended to use functools.cached_property right?

[bveeramani]

I wonder if the functools.cache here has no effect at all. As far as I know, functools.cache only caches function arguments, but this method has no arguments except for self.

The intention is that we'd only compute the values once per instance (i.e., for each value of self). Is that not the behavior with functools.cache?

[MortalHappiness]

@bveeramani In Python, it’s more common to use functools.cached_property to cache methods with no arguments.

See https://docs.python.org/3/faq/programming.html#faq-cache-method-calls for details.