Gemini client

[marouanetalaa]

Description

Implement a Gemini LLMClient and test for it.

Related Issue

Implement a Gemini LLMClient #1901

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)
• [x] 🚀 New feature (non-breaking change which adds functionality)
• [ ] 💥 Breaking change (fix or feature that would cause existing functionality to change)
• [ ] 🔐 Security fix

Checklist

• [x] I've read the CODE_OF_CONDUCT.md document.
• [x] I've read the CONTRIBUTING.md guide.
• [x] 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)