"Let the optimizer find the optimal imputer" in "Classification AutoML with imputation" cannot recognize NaN at first

[williamty]

If don't predefine imputer, "let the optimizer find the optimal imputer" in "Classification AutoML with imputation", the optimal imputer will encounter a problem that it "does not accept missing values encoded as NaN natively". Shouldn't it first judge whether there is null data in the dataset? Otherwise what's the meaning of "optimal"?