alwaysmpe

This is also inconvenient when using zip with any_view for type erasure, eg [this](https://godbolt.org/z/Prhnz3fsb)

For large datasets the code isn't evaluating every possible partition (presumably due to performance). Instead it's using mean and +/- 1-3 std deviations. This subsampling is implemented in ‎[processContinuousFeatures](https://github.com/serengil/chefboost/blob/4f9ce13061558769e38a6a1938d7b0118f9ab9bf/chefboost/training/Preprocess.py#L8).