Input / Outputs for ColumnTransformers not captured

[Ennosigaeon]

I try to capture the outputs of Estimators in a ColumnTransformer using alter_pipeline_for_debugging and enumerate_pipeline_models. Yet, all inputs and outputs for the Estimatorss in a ColumnTransformer are not captured.

In enumerate_pipeline_models, all transformers are extracted from ColumnTransformers. Yet, for the actual transformation the field transformers_ is used (see here and here).

I think, replacing enumerate(pipe.transformers) with enumerate(pipe.transformers_) should solve this issue. If you would like to, I can provide an according PR.

[sdpython]

It would be a great help if you could provide a PR, even incomplete.