Implement Mixup in Numpy, PyTorch, and TensorFlow

[f4str]

Description

Implementation of the Mixup data augmentation defense in the Numpy, PyTorch, and TensorFlow frameworks.

Fixes # (issue)

Type of change

Please check all relevant options.

• Improvement (non-breaking)
• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing

Please describe the tests that you ran to verify your changes. Consider listing any relevant details of your test configuration.

• Tests for the Mixup preprocessor in Numpy
• Tests for the Mixup preprocessor in PyTorch
• Tests for the Mixup preprocessor in TensorFlow

Test Configuration:

• OS
• Python version
• ART version or commit number
• TensorFlow / Keras / PyTorch / MXNet version

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov-commenter]

Codecov Report

Merging #1885 (cb5a91a) into dev_1.13.0 (89bf92f) will increase coverage by 0.08%.
The diff coverage is 90.24%.

@@              Coverage Diff               @@
##           dev_1.13.0    #1885      +/-   ##
==============================================
+ Coverage       85.87%   85.95%   +0.08%     
==============================================
  Files             248      254       +6     
  Lines           23310    23587     +277     
  Branches         4212     4268      +56     
==============================================
+ Hits            20017    20274     +257     
- Misses           2230     2239       +9     
- Partials         1063     1074      +11     

Impacted Files	Coverage Δ
art/defences/preprocessor/mixup/mixup.py	90.00% <90.00%> (ø)
art/defences/preprocessor/mixup/mixup_pytorch.py	90.00% <90.00%> (ø)
...rt/defences/preprocessor/mixup/mixup_tensorflow.py	90.00% <90.00%> (ø)
art/defences/preprocessor/__init__.py	100.00% <100.00%> (ø)
art/estimators/certification/abstain.py	90.90% <0.00%> (-9.10%)	⬇️
art/estimators/poison_mitigation/strip/strip.py	94.44% <0.00%> (-5.56%)	⬇️
art/attacks/evasion/boundary.py	92.77% <0.00%> (-1.21%)	⬇️
.../defences/preprocessor/cutout/cutout_tensorflow.py	97.77% <0.00%> (ø)
art/defences/preprocessor/cutout/cutout_pytorch.py	98.11% <0.00%> (ø)
... and 1 more

[lgtm-com]

This pull request introduces 2 alerts when merging f5a8697 into 20b01a3 - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging f5a8697 into 89bf92f - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging 998761d into 89bf92f - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging d0b58f8 into 89bf92f - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging 9eb621f into 89bf92f - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging d8a9783 into 89bf92f - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 4 alerts when merging 3314d6c into 89bf92f - view on LGTM.com

new alerts:

• 2 for Wrong name for an argument in a call
• 2 for Module is imported more than once

[lgtm-com]

This pull request introduces 2 alerts when merging cb5a91a into c366b1d - view on LGTM.com

new alerts:

• 2 for Module is imported more than once

[beat-buesser]

Hi @f4str Thank you very much! LGTM