Please note in the documentation (or in the constructor) that closures must be enabled

[ABotond]

Hi,

I had today a relatively long debug session, after I've upgraded my Pytorch Lightning installation, that the training_step wasn't called.

It finally turned out, that the problem was that the "closure" argument is not used in the step function (it is commented out - as also noted in the source code).

However, as it is apparently required by some libraries and is also recommended by the official PyTorch guidelines, it would be great if it would be better documented, that people might need to enable these lines.

Thanks in advance.