Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> x = torch.randn(3, 4)
  >>> x
  tensor([[ 0.1427,  0.0231, -0.5414, -1.0009],
          [-0.4664,  0.2647, -0.1228, -1.1068],
          [-1.1734, -0.6571,  0.7230, -0.6004]])
  >>> indices = torch.tensor([0, 2])
  >>> torch.index_select(x, 0, indices)
  tensor([[ 0.1427,  0.0231, -0.5414, -1.0009],
          [-1.1734, -0.6571,  0.7230, -0.6004]])
  >>> torch.index_select(x, 1, indices)
  tensor([[ 0.1427, -0.5414],
          [-0.4664, -0.1228],
          [-1.1734,  0.7230]])
