Hi, the issue lies in the line:
loss, current = loss.item()
loss.item() gives you a single float value. And it cannot be packed to two values, loss, current. The correct way would be:
loss = loss.item()
If you want a more in depth tutorial please refer to this example over here.
If you want to read more about loss.item() please refer this.
Regarding, it taking 3.5 hours. I thinking you are not using GPUs in google colab. Computations would be much faster in GPU.