[DOC] Python 3.14 issues

[HaoZeke]

Location of the issue

N/A.

Description of the issue

gh repo clone metatensor/metatrain
cd metatrain
uv venv -p 3.14
. .venv/bin/activate
uv pip install -e .
mtt export https://huggingface.co/lab-cosmo/upet/resolve/main/models/pet-mad-s-v1.0.2.ckpt

Which generates an error log.

`error.log`

❯ cat error.log
Traceback (most recent call last):
  File "/home/rgoswami/Git/Github/epfl/pixi_envs/orgs/metatensor/metatrain/metatrain/src/metatrain/__main__.py", line 95, in main
    export_model(**args.__dict__)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/rgoswami/Git/Github/epfl/pixi_envs/orgs/metatensor/metatrain/metatrain/src/metatrain/cli/export.py", line 221, in export_model
    model.save(path, collect_extensions=extensions_path)
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/metatomic/torch/model.py", line 539, in save
    module = torch.jit.script(module)
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/torch/jit/_script.py", line 1437, in script
    ret = _script_impl(
        obj=obj,
    ...<3 lines>...
        example_inputs=example_inputs,
    )
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/torch/jit/_script.py", line 1146, in _script_impl
    return torch.jit._recursive.create_script_module(
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        obj, torch.jit._recursive.infer_methods_to_compile
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/torch/jit/_recursive.py", line 556, in create_script_module
    AttributeTypeIsSupportedChecker().check(nn_module)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/torch/jit/_check.py", line 77, in check
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rgoswami/Git/Github/epfl/tmp/.venv/lib/python3.14/site-packages/torch/nn/modules/module.py", line 1964, in __getattr__
    raise AttributeError(
        f"'{type(self).__name__}' object has no attribute '{name}'"
    )
AttributeError: 'AtomisticModel' object has no attribute '__annotations__'. Did you mean: '__annotate_func__'?

Suggested fix or improvement (optional)

This actually is a version error, for example, downgrading to Python 3.12 works.

Additional context

I don't think it's much of a bug, but we might want to have better logging / documentation.

[Luthaf]

This is the same as lab-cosmo/upet#80, and comes from torch 2.9 not being compatible with python 3.14. This should be fixed when we release new versions that work with torch 2.10.