Error in dimension of image tensor

[Brian Robinson]

First of all, thanks for taking the time to put this pytorch implementation together. I am getting the following error. Also can you explain what the purpose of the torch.cat line is?

Traceback (most recent call last):
File "train.py", line 133, in
train(opt)
File "train.py", line 58, in train
state = torch.cat(tuple(image for _ in range(4)))[None, :, :, :]
IndexError: too many indices for tensor of dimension 2