`experimental` decorator breaks class documentation.

The experimental decorator used on classes break documentation. This could be one manifestation but there is an issue with how the documentation including type hints are propagated to the decorated class. This does not apply for free functions.

See https://github.com/optuna/optuna/pull/1265#issuecomment-633195955 for how it may break.

Expected behavior

Class documentation should not be altered by applying the experimental decorator.

Steps to reproduce

1. Apply the experimental decorator to a class.
2. Build the document (cd docs && make html)
3. Open the rendered documentation and note that the class signatures is broken.

Additional context (optional)

• An issue regarding the indentation https://github.com/optuna/optuna/issues/1213.

[harupy]

It looks fine. I’ll submit a PR.

Before:

After:

[harupy]

Decorating wrapped_init by functools.wraps and removing func_spec_str should solve this issue.