feat: customAttackAndDefense

[Realvelocity]

📦 Pull Request Template

Thank you for your contribution! Please complete the checklist and provide relevant details below to help us review your PR effectively.

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📋 Summary

This PR adds a custom attack (MyCustomAttack) and a custom defense (MyCustomDefense) implementation to the PyGIP framework. It also includes example scripts under examples/ for running these attacks and defenses on datasets.

🧪 Related Issues

Implements the custom attack/defense framework as described in the repository README

✅ Checklist

• My code follows the project's coding style
• I have tested the changes and verified that they work
• I have added necessary documentation (if applicable)
• I have linked related issues above (if any)
• The PR is made from a feature branch, not main

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🧠 Additional Context (Optional)

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