PReLU rank 3 or rank 5 input requires all values of alpha to be the same?

## ❓Question

Hi, I was trying to convert a traced PyTorch model with a `PReLU` module and one of its components looks like this:
```py
Block(
(conv1): Conv1d(1, 32, kernel_size=(5,), stride=(1,), bias=False)
(bn): BatchNorm1d(32, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(relu): PReLU(num_parameters=32)
(res): Conv1d(1, 32, kernel_size=(1,), stride=(1,), bias=False)
)
```

When I convert the model though, I get this error:
```py
ValueError: prelu op: rank 3 or rank 5 input is only supported when all the values of alpha are same,which is not the case here
```

I patched out the check locally and it allows the model to successfully export and perform an inference run too, though I haven't checked if it yields legible output.

Is there documentation on why this restriction is in place?