title: Stacking tensors in a list of tuples of tensors
body: <p>I have a list of tuples of PyTorch tensors. It looks like this:</p>
  
  <pre><code>[
      (tensor([1, 2, 3]),  tensor([4, 5, 6, 7]),  tensor([8])),
      (tensor([9, 10,11]), tensor([11,12,13,14]), tensor([15])),
      (tensor([16,17,18]), tensor([19,20,21,22]), tensor([23])),
      ...
  ]
  </code></pre>
  
  <p>Tensors in each column (that is, tensors that position k of their respective tuple) share the same shape. I want to stack the tensors in each column so that I end up with a single tuple, each value being the tensors concatenated along the dimension of the column. </p>
  
  <p>In this case, the output tuple would have three values, and look like this:</p>
  
  <pre><code>(
   tensor([[1,2,3], [9,10,11], [16,17,18]]),
  
   tensor([[4,5,6,7], [11,12,13,14], [19,20,21,22]],
  
   tensor([[8],[15],[23])
  )
  </code></pre>
  
  <p>This is a made-up example. I want to do this for tuples of any length, and tensors of arbitrary size. What is the best way to do this type of concatenation quickly using PyTorch?</p>