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I wonder if I can have feedback before I add/fix more tests.
@glemaitre

I see that we have to handle one specific case:

We have an internal PassThrough transformer that forward the input feature as-is and this it means that we should mention that the output feature are the same as n_features_in_.

I find the block a bit big, it takes as much space as the estimator itself. I was also thinking that having the input features would be nice but then it really starts to take a lot of space around the estimator. So I wondered if the features could be intermediate blocks in the diagram, representing both the output features from the previous estimator and the input features for the next estimator. Something like this

This way the diagram alternates estimator blocks and data blocks
Then the text would be different obviously, like "16 features", or even the full shape ?

In addition, in this PR or in a following one, the data block could be unfold to show the feature names if available.

One feedback of @ogrisel IRL is to directly show the feature names using the same pattern than "Parameters".

I personally agree with @jeremiedbb feedback: I would like something smaller. Also write now, we have to mention "output features" instead of simply "features" because of the ambiguity input/output when attached to the estimator. So the proposal to make the "feature" being blocks leaving on their own is nice I think because there is not ambiguity anymore.

I'll work on this, thanks for the feedback. Just:

One feedback of @ogrisel IRL is to directly show the feature names using the same pattern than "Parameters".

Should I add the feature names on this PR? I remember @glemaitre saying that they should be added on a separate PR.

Should I add the feature names on this PR?

I want to dissociate it at first but since we are going to create a new block, it might be better to have directly the feature names as well.