Use raw string for docstrings containing escape sequences

[kmaehashi]

Hello, my first pull-request here. 😃
When running array-api-tests against CuPy, I experienced the following error:

+ ARRAY_API_TESTS_MODULE=cupy.array_api
+ pytest
ImportError while loading conftest '/tmp/tmp.IchRO6sbmt/array-api-tests/conftest.py'.
conftest.py:7: in <module>
    from array_api_tests import _array_module as xp
array_api_tests/__init__.py:6: in <module>
    from ._array_module import mod as _xp
array_api_tests/_array_module.py:4: in <module>
    from . import stubs
array_api_tests/stubs.py:30: in <module>
    name_to_mod[name] = import_module(f"signatures.{name}")
E     File "/tmp/tmp.IchRO6sbmt/array-api-tests/array-api/spec/API_specification/signatures/elementwise_functions.py", line 601
E       """
E       ^
E   SyntaxError: invalid escape sequence \s

This was because there are unescaped uses of \ in several docstrings of array-api code, and CuPy runs tests with error::DeprecationWarning warning filter which strictly checks the invalid escape sequences.

This PR fixes the issue by using raw string for such docstrings, in the same way as done in cholesky:

array-api/spec/API_specification/array_api/linalg.py

Lines 4 to 5 in 6a35bc1

	def cholesky(x: array, /, *, upper: bool = False) -> array:
	r"""

I confirmed there are no invalid escape sequences anymore:

find . -name "*.pyc" -delete
python -W error::DeprecationWarning -m compileall spec

Thanks.

[honno]

Yep LGTM, thanks!

Note I won't be able to update array-api-tests yet to use this immediately, as this repos changed a fair bit in the last ~month and so I need to update a few things to support it again. Probably low-priority for now 😕

[leofang]

Right we fixed the signatures to make sure they can be referenced in Sphinx (#430). But, @honno why is it a low priority? It sounds like after the signature fix the array-api tests just cannot be run? Did it pin this repo as a submodule?

[honno]

Did it pin this repo as a submodule?

Yep.

Just hacking array-api-tests for this PR to be parsed I noticed a fair few spec changes that mess with prior assumptions for other parts of the test suite—I'll want to fix these properly, but it's not necessary for testing v1 Array API namespaces, and testing v2 namespaces isn't useful for at least another month. I'll definitely get round to it, it's just I have dataframe work which is high priority for at least the next 2 weeks.

[leofang]

We'll backport #430 to v1 so it's still needed, but I agree if array-api is pinned it's not urgent.

[kgryte]

LGTM. Thanks, @kmaehashi!

[jakevdp]

I'm running into this issue when attempting to test against array-api@2022-12. Any suggestions for how to proceed? Is there any safe tag to checkout if I want to test version 2022-12?

$ Run pytest --ci array-api-tests/array_api_tests/
ImportError while loading conftest '/home/runner/work/jax/jax/array-api-tests/conftest.py'.
array-api-tests/conftest.py:9: in <module>
    from array_api_tests import _array_module as xp
array-api-tests/array_api_tests/__init__.py:8: in <module>
    from ._array_module import mod as _xp
array-api-tests/array_api_tests/_array_module.py:4: in <module>
    from . import stubs
array-api-tests/array_api_tests/stubs.py:31: in <module>
    name_to_mod[name] = import_module(f"signatures.{name}")
E     File "/home/runner/work/jax/jax/array-api-tests/array-api/spec/API_specification/signatures/linalg.py", line 44[7](https://github.com/google/jax/actions/runs/5073141741/jobs/9111776151?pr=16099#step:6:8)
E       """
E       ^^^
E   SyntaxError: invalid escape sequence '\*'

[jakevdp]

Opened an issue in #631