Implementation error of GATConv

[linfeng-du]

The message function of GATConv in chem/model.py writes
image
However, I think the alpha should be normalized w.r.t edge_index[1] (dst nodes) instead of edge_index[0] (src nodes) so that it is normalized among nodes connecting to a dst.

Although for undirected graphs, what calculated after scatter operations woule be the same, yet different indexing has different meaning (edge_index[0] and edge_index[1])

Consider this simple case, edge_index[1] gives the desired result