Hello, I have some questions about torch.unique().

For a cpu tensor:

```
input = torch.tensor([[2,5,7,6],[9,7,4,8],[1,3,2,3],[2,5,7,6]])
input
tensor([[2, 5, 7, 6],
[9, 7, 4, 8],
[1, 3, 2, 3],
[2, 5, 7, 6]])
torch.unique(input)
tensor([3, 1, 8, 4, 9, 6, 7, 5, 2])
torch.unique(input, sorted=True)
tensor([1, 2, 3, 4, 5, 6, 7, 8, 9])
torch.unique(input, dim=0)
tensor([[1, 3, 2, 3],
[2, 5, 7, 6],
[9, 7, 4, 8]])
torch.unique(input, sorted=True, dim=0)
tensor([[1, 3, 2, 3],
[2, 5, 7, 6],
[9, 7, 4, 8]])
torch.unique(input, sorted=False, dim=0)
tensor([[1, 3, 2, 3],
[2, 5, 7, 6],
[9, 7, 4, 8]])
```

I note that for torch.unique the default sorted=True in official documentation (https://pytorch.org/docs/stable/_modules/torch/functional.html#unique). However, when using torch.unique(input), the output is unsorted. When I use torch.unique(input, sorted=False, dim=0), the output is still sorted.

Furthermore, I also test a gpu tensor, and find all the output results are sorted regardless of whether setting sorted=True or False.

Why? There seems something wrong about it?