Worked on code quality improvements in the optuna/optuna repository, focusing on optimizing type-checked imports within a core visualization module. Refactored the import structure in Python by moving type-only imports under the TYPE_CHECKING guard, which reduced runtime overhead and improved maintainability. This approach enhanced type checking without impacting performance, specifically targeting the visualization/_param_importances.py file. The work leveraged Python and software development best practices, with an emphasis on type checking to ensure code clarity and efficiency. No bugs were addressed during this period, and the primary contribution centered on a single feature aimed at improving codebase quality and runtime efficiency.