Release Notes
1. **Enhancements in the `CrossValidator` class**:
- Added `save` and `load` methods to allow saving and loading validator instances.
- Introduced the `plot_score` method to visualize scores using boxplot, line plot, or histogram.
- Added the `ifit` method, a lazy version of the `fit` method.
- Added the `cv_results_` attribute to store a dictionary of calculated metrics for each fold.
- Added the `models_` attribute to store fitted models for each fold.
2. **Updates in the `OptunaTuneCV` class**:
- Added support for the `trial_timeout` parameter when `parallel_mode=True`.