Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> a = torch.randn(3, 3)
  >>> a
  tensor([[ 0.2309,  0.5207,  2.0049],
          [ 0.2072, -1.0680,  0.6602],
          [ 0.3480, -0.5211, -0.4573]])
  >>> torch.triu(a)
  tensor([[ 0.2309,  0.5207,  2.0049],
          [ 0.0000, -1.0680,  0.6602],
          [ 0.0000,  0.0000, -0.4573]])
  >>> torch.triu(a, diagonal=1)
  tensor([[ 0.0000,  0.5207,  2.0049],
          [ 0.0000,  0.0000,  0.6602],
          [ 0.0000,  0.0000,  0.0000]])
  >>> torch.triu(a, diagonal=-1)
  tensor([[ 0.2309,  0.5207,  2.0049],
          [ 0.2072, -1.0680,  0.6602],
          [ 0.0000, -0.5211, -0.4573]])

  >>> b = torch.randn(4, 6)
  >>> b
  tensor([[ 0.5876, -0.0794, -1.8373,  0.6654,  0.2604,  1.5235],
          [-0.2447,  0.9556, -1.2919,  1.3378, -0.1768, -1.0857],
          [ 0.4333,  0.3146,  0.6576, -1.0432,  0.9348, -0.4410],
