LightGBM.cv时，feature_pre_filter和min_data_in_leaf相互矛盾

当LightGBM.cv时，如果min_data_in_leaf设置的值比默认值（20）小的时候，就会报错：

LightGBMError: Reducing `min_data_in_leaf` with `feature_pre_filter=true` may cause unexpected behaviour for features that were pre-filtered by the larger `min_data_in_leaf`.
You need to set `feature_pre_filter=false` to dynamically change the `min_data_in_leaf`.

 

在网上查了很多资料，说是要在dataset之前设置feature_pre_filter，但是有的人又说这个参数已经删除了，翻看官网也没有看到很好的解决方法：https://github.com/optuna/optuna/issues/1718

反正我们就默认这个参数feature_pre_filter已经删除了，如果我们调参时min_data_in_leaf 的最佳值大于20时，就可以保留min_data_in_leaf参数，如果小于时，就删除这个参数。就可以运行了