code: def gcn_reduce(self, node):
      return {"x": node.mailbox["m"].sum(dim=1) * node.data["norm"]}
  
imports: import dgl.function
  import torch
  import torch.nn.functional
  from torch.nn import Parameter
  from torch_geometric.nn.inits import glorot, zeros
label_desc: Use image node_id 4 for calling the GCNConv obj's underlying member method code with example usage: obj.gcn_reduce(node) and returns: dict