There is a convention that the labels should be a 1-dimensional array, not a 2-dimensional array. I.e., right now, you have 200x1 as the label array, but it should be simply 200. Try
loss = loss_fn(outputs, labels.view(-1).long())

instead of
loss = loss_fn(outputs, labels.long())

This be able to solve your issue. Btw I see that you are using Variable etc, which is old PyTorch code (it has been deprecated and removed in newer versions) – just wanted to mention that in case you encounter errors related to that later on when you update your PyTorch installation to the current ones.