How to get the message being passed in torch geometric?

Question

I am working on a project with GNN with Torch Geometric. I wanted to try the layer norm.MessageNorm, however it requires in the forward step as inputs the following (as of documentation):

• x (torch.Tensor) – The source tensor.
• msg (torch.Tensor) – The message tensor
• p (float, optional) – The norm to use for normalization. (default: 2.0)

x will be as usual the output of the previous layer, however, where do I get the msg needed?

Thanks a lot in advance