Add numerical perturbation detector

[Kranium2002]

Description

This PR adds the numerical perturbation detector feature to robustness detector. This PR is still a work in progress.

The detector will perturb the values by 1 percent and then check for errors in classification mode and for regression the model flags any error which is 5% away from the real value. This could be made so that the user can adjust these percentages but for now this is fixed. Review needed on this.

Related Issue

closes #1846

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

Checklist

• I've read the CODE_OF_CONDUCT.md document.
• I've read the CONTRIBUTING.md guide.
• I've written tests for all new methods and classes that I created.
• I've written the docstring in Google format for all the methods and classes that I used.
• I've updated the pdm.lock running pdm update-lock (only applicable when pyproject.toml has been
  modified)

[Kranium2002]

@kevinmessiaen Please review

[alexcombessie]

Hey @henchaves - Would you have some bandwidth to review this PR ?

[Kranium2002]

@henchaves Did you get a chance to look at this? Do I need to make any changes?

[henchaves]

Hello @Kranium2002,
A researcher will review your PR as soon, to check if something is still needed in the algorithm logic.
After that, me or @kevinmessiaen will review the code itself. Sorry for the delay!

[mattbit]

Hi @Kranium2002, thanks so much for the contribution! I think numerical perturbation is a great addition to the library.

I've noted a few issues with the proposed implementation, in summary:

• We should check for features not only based on their data type, but column type (sometimes we have categorical features represented as numbers, but we don't want to apply the numerical perturbation to those)
• The perturbation functions used should be defined as instances of TranformationFunction (the same we use for text perturbation or other transformations)
• We need to be careful not to alter the underlying data type. Certain transformations should be applied depending on whether the feature has integer or float values (e.g. we don't want to add Gaussian noise to integers)

I also feel there is a lot of redundancy between the BaseNumericalPerturbationDetector calss and BaseTextPerturbationDetector. It's probably worth refactoring this to have a common base class covering the shared behavior instead of duplicating code — @henchaves can help with that ;)

[mattbit]

These should be proper transformation functions (extending TransformationFunction).

IMPORTANT: all of these perturbations assume that the numerical values are floats. This is not always the case, integer features are common: when such data types are present we must not alter that. Applying the transformations above (for example Gaussian noise) to an integer feature like num_passengers would silently convert the data type to float, potentially breaking the model inference.

[Kranium2002]

So how do you suggest I check perturbation for integer data?

[Kranium2002]

Thank you for your review @mattbit I will work on this on the weekend.