def _check_optimizable_historical_forecasts(
        self,
        forecast_horizon: int,
        retrain: Union[bool, int, Callable[..., bool]],
        show_warnings: bool,
    ) -> bool:
        """By default, historical forecasts cannot be optimized"""
        return False
By default, historical forecasts cannot be optimized
darts/models/forecasting/forecasting_model.py