In the basic variant of GCN we have the following:
Here we aggregate the information from the adjacent node and pass it to a neural network, then transform our own information and add them all.
But the main question is: how can we ensure that $W_{k}(\sum(\frac{h_k}{N(V)})$ will be the same size as $B_{k}h_{v}$ and does $B_{k}$ emply another neural network?