Unguarded "from typing_extensions import Self" introduced by #10359

[sjperkins]

What happened?

The following PR:

• Enforce ruff/flake8-pyi rules (PYI) #10359

introduced an unguarded "from typing_extension import Self"

xarray/xarray/core/accessor_dt.py

Line 8 in f1a2c08

from typing_extensions import Self

whereas in other locations such imports are guarded

xarray/xarray/core/types.py

Lines 22 to 33 in f1a2c08

	try:
	if sys.version_info >= (3, 11):
	from typing import Self, TypeAlias
	else:
	from typing import TypeAlias
	from typing_extensions import Self
	except ImportError:
	if TYPE_CHECKING:
	raise
	else:
	Self: Any = None

I've seen this fail on Python 3.11 if typing_extensions is not manually installed alongside xarray

What did you expect to happen?

No response

Minimal Complete Verifiable Example

On the main branch

 $ python
Python 3.11.13 (main, Jun  4 2025, 08:57:30) [GCC 13.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import xarray
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/simon/code/xarray/xarray/__init__.py", line 3, in <module>
    from xarray import coders, groupers, testing, tutorial, ufuncs
  File "/home/simon/code/xarray/xarray/groupers.py", line 33, in <module>
    from xarray.core.dataarray import DataArray
  File "/home/simon/code/xarray/xarray/core/dataarray.py", line 28, in <module>
    from xarray.core.accessor_dt import CombinedDatetimelikeAccessor
  File "/home/simon/code/xarray/xarray/core/accessor_dt.py", line 8, in <module>
    from typing_extensions import Self
ModuleNotFoundError: No module named 'typing_extensions'
>>> 

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

Anything else we need to know?

No response

Environment

[sjperkins]

• Related to Release workflows: always check that the built dist is valid. #10408