code: def rgcn_reduce(self, node):
      return {"x": node.mailbox["m"].sum(dim=1)}
  
imports: import dgl.function
  import torch
  import torch.nn.functional
  from torch.nn import Parameter
  from torch_geometric.nn.inits import uniform
label_desc: Use image node_id 3 for calling the RGCNConv obj's underlying member method code with example usage: obj.rgcn_reduce(node) and returns: dict