Unable to use `_` operator in this example
```Nim
import arraymancer

proc foo[T](t: Tensor[T], x: int): Tensor[T] =
  t.unsafeSlice(x, _, _).unsafeReshape([t.shape[1], t.shape[2]])

echo zeros([2,2,2], int).foo(1)
```
in global_config.nim it works.

```
test2.nim(6, 25) template/generic instantiation from here
test2.nim(4, 25) Error: type mismatch: got (int, array[0..1, int])
but expected one of: 
proc unsafeReshape(t: Tensor; new_shape: varargs[int]): Tensor
```