Hello,

I wonder if it is possible to set learning rates for each channel of the weight in a certain conv layer? I wrote an example but it would raise an error.

```
# e.g.
class Model(nn.Module):
def __init__(self):
super(Model, self).__init__()
self.conv = nn.Conv2d(3, 8, kernel_size=1, padding=0, stride=1, bias=False)
def forward(self, x):
return self.conv(x)
model = Model()
print(model.conv.weight.shape) # torch.Size([8, 3, 1, 1])
lr = [0.01* i for i in range(1, model.conv.weight.shape[0] + 1)] # [0.01, 0.02, ..., 0.08]
torch.optim.Adam(([{'params': p, 'lr': l} for p,l in zip(model.conv.weight, lr)])
# ValueError: can't optimize a non-leaf Tensor
```

Thanks!