Ah, you might be right. In that case @laurent-dinh might want to fix this line https://github.com/axeldavy/pylearn2/blob/CompositeLayerComplete/pylearn2/models/mlp.py#L160 which says that it is.

Just had a closer look and it seems like `get_monitoring_channels` is one of the MLP parts that is hardcoded to assume there is only one input and one output. I'd say leave it like this for now, but maybe add a comment that it should be fixed if/when support for multiple inputs and outputs is comes?