Worked on the optuna/optuna repository to improve code quality by refactoring import statements in the test suite, specifically targeting tests/visualization_tests/test_timeline.py. The approach involved leveraging Python’s TYPE_CHECKING to restructure imports, which helped avoid circular dependencies and reduced import-time overhead. This change enhanced startup performance and improved the reliability of test execution, making the codebase more maintainable for future development. The update was backward-compatible and laid the foundation for safer refactoring and better static analysis. The work demonstrated skills in Python, software development, and testing, with a focus on maintainability and robust engineering practices within the project.