Summary of Changes

Hello @daniel-sanche, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request, initiated by an automated librarian update, primarily focuses on enhancing the robustness and maintainability of the Bigtable client libraries. It introduces crucial runtime environment validation checks for Python and key dependencies, alongside a significant refactoring of the mTLS client certificate handling logic for improved clarity and consistency. Additionally, it cleans up old code transformation scripts and marks generated files, streamlining the development process.

Highlights

• Automated Librarian Image Update: The pull request updates the python-librarian-generator image to a new SHA256 hash, indicating an automated update of the underlying code generation tool.
• Runtime Environment and Dependency Checks: New code has been introduced in the __init__.py files for bigtable_admin_v2 and bigtable_v2 to perform runtime checks for the Python version (warning for versions older than 3.9 and for 3.9 itself) and the google.protobuf dependency version (warning for versions older than 4.25.8). This logic conditionally uses google.api_core helper functions or implements manual checks if those are unavailable.
• Refactored mTLS Client Certificate Handling: A new static method _use_client_cert_effective has been added to the Bigtable client classes (BigtableInstanceAdminClient, BaseBigtableTableAdminClient, BigtableClient). This method centralizes the logic for determining whether client certificates should be used for mTLS, checking for google-auth's should_use_client_cert and falling back to the GOOGLE_API_USE_CLIENT_CERTIFICATE environment variable.
• Removal of Keyword Fixup Scripts: Two Python scripts, scripts/fixup_bigtable_admin_v2_keywords.py and scripts/fixup_bigtable_v2_keywords.py, which were likely used for code transformation, have been removed.
• Generated File Markers: Comments indicating that noxfile.py and setup.py are generated files and should not be edited directly have been added, pointing to .librarian/generator-input as the source of truth.
• Comprehensive Test Updates: Unit tests for bigtable_admin_v2 and bigtable_v2 have been updated to reflect the new mTLS client certificate determination logic, including new test cases for _use_client_cert_effective and adjustments to existing environment variable tests.