Consider following matrixes

```
>>> a = torch.Tensor([[1,2,3],[4,5,6], [7,8,9]])
>>> a
tensor([[1., 2., 3.],
[4., 5., 6.],
[7., 8., 9.]])
>>> b = torch.tensor([[1,1],[1,1]])
>>> b
tensor([[1, 1],
[1, 1]])
```

I want to replace 4 elements in a with b where their indices are specified in X = [0,2] and Y = [0,2]

To have:

```
>>>a
tensor([[1., 2., 1.],
[4., 5., 6.],
[1., 8., 1.]])
```