Add str method to datamodule

[MrWhatZitToYaa]

What does this PR do?

Added a str function to the DataModule in order to be able to print Datasets included in the module instead of an adress.

Fixes #9947

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📚 Documentation preview 📚: https://pytorch-lightning--20301.org.readthedocs.build/en/20301/

[MrWhatZitToYaa]

Will add documentation once code is fixed

[MrWhatZitToYaa]

I have been waiting for quite some time. How do I go on? Do I just wait some more until someone looks at this?

[lantiga]

hey @MrWhatZitToYaa thanks for taking this up and sorry for the wait

can you add a bit more detail on what do we think it's good printing from a datamodule?

the original design in #9947 was a bit different, as was #9967, but happy to consider alternatives after there's some discussion on the rationale

[MrWhatZitToYaa]

hey @MrWhatZitToYaa thanks for taking this up and sorry for the wait

can you add a bit more detail on what do we think it's good printing from a datamodule?

the original design in #9947 was a bit different, as was #9967, but happy to consider alternatives after there's some discussion on the rationale

The idea originally came to me when I had to to use the Datamodule to implement some datasets we have in our lab. It was really annoying to deal with the fact that you never really know what you are dealing with and makes debugging really hard. I talked to some colleagues and they agreed that they ran into the same problem. That's why I would like to add a str functionality for the Datamodule: primarily for debugging / logging.
I think the simplest approach is to scan the whole module for instances of datasets and then return a string where each line contains the name of the dataset and the length if it is available. This would be a big quality of life improvement when dealing with / constructing Datamodules.