torch.vstack
torch.vstack(tensors, *, out=None) -> Tensor
Stack tensors in sequence vertically (row wise).
This is equivalent to concatenation along the first axis after all
   1-D tensors have been reshaped by "torch.atleast_2d()".
Parameters:
      tensors (sequence of Tensors) -- sequence of tensors to
      concatenate
Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> a = torch.tensor([1, 2, 3])
  >>> b = torch.tensor([4, 5, 6])
  >>> torch.vstack((a,b))
  tensor([[1, 2, 3],
          [4, 5, 6]])
  >>> a = torch.tensor([[1],[2],[3]])
  >>> b = torch.tensor([[4],[5],[6]])
  >>> torch.vstack((a,b))
  tensor([[1],
          [2],
          [3],
          [4],
          [5],
          [6]])
