Allow to periodically save with any function

[basnijholt]

Description

This allows saving with e.g., pandas, like:

def save_dataframe(
    fname: str | list[str] | tuple[str, ...], **to_dataframe_kwargs: Any
) -> Callable[[BaseLearner], None]:
    def save(learner):
        df = learner.to_dataframe(**to_dataframe_kwargs)
        fname_df = fname_to_dataframe(fname)
        df.to_parquet(fname_df)

    return save

save_task = runner.start_periodic_saving(interval=5, method=save_dataframe("test.parquet"))

Checklist

• Fixed style issues using pre-commit run --all (first install using pip install pre-commit)
• pytest passed

Type of change

Check relevant option(s).

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• (Code) style fix or documentation update
• This change requires a documentation update