[BUG] Importing OpTree 0.12.0 raises `FutureWarning`s (regression)

Required prerequisites

[X] I have read the documentation https://optree.readthedocs.io.
[X] I have searched the Issue Tracker that this hasn't already been reported. (comment there if it has.)

What version of OpTree are you using?

0.12.0

System information

OpTree was installed via pip install optree==0.12.0.

>>> import sys, optree
>>> print(sys.version, sys.platform)
3.12.4 (tags/v3.12.4:8e8a4ba, Jun  6 2024, 19:30:16) [MSC v.1940 64 bit (AMD64)] win32
>>> print(optree.__version__)
0.12.0

Problem description

Just running import optree raises FutureWarnings since 0.12.0, which breaks our tests. Warnings are suppressed in default Python REPLs, so you have to run Python with python -W default or python -W error to see it.

The warning happens with OpTree 0.12.0, it doesn't happen with 0.11.0.

Since OpTree is a dependency of Keras, I could imagine this affects others as well.

Reproducible example code

python -W error -c 'import optree'

or (without tracebacks)

import warnings
warnings.simplefilter("default")
import optree

Traceback

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File ".venv\Lib\site-packages\optree\__init__.py", line 17, in <module>
    from optree import accessor, functools, integration, typing
  File ".venv\Lib\site-packages\optree\functools.py", line 24, in <module>
    from optree import registry
  File ".venv\Lib\site-packages\optree\registry.py", line 738, in <module>
    class GetitemKeyPathEntry(KeyPathEntry):
  File ".venv\Lib\site-packages\typing_extensions.py", line 2839, in __init_subclass__
    warnings.warn(msg, category=category, stacklevel=stacklevel + 1)
FutureWarning: The key path API is deprecated and will be removed in a future version. Please use the accessor API instead.

Expected behavior

No warnings are raised when importing OpTree.

Additional context

No response

metaopt / optree