title: Use of torch.stack()
body: <pre><code>t1 = torch.tensor([1,2,3])
  t2 = torch.tensor([4,5,6])
  t3 = torch.tensor([7,8,9])
  
  torch.stack((t1,t2,t3),dim=1)
  </code></pre>
  <p>When implementing the torch.stack(), I can't understand how stacking is done for different dim.
  Here stacking is done for columns but I can't understand the details as to how it is done. It becomes more complicated dealing with 2-d or 3-D tensors.</p>
  <pre><code>tensor([[1, 4, 7],
          [2, 5, 8],
          [3, 6, 9]])
  </code></pre>