code: def gcn_reduce(node):
      accum = mx.nd.sum(node.mailbox["m"], 1) * node.data["norm"]
      return {"h": accum}
  
file_path: dgl/examples/mxnet/gcn/gcn_mp.py
imports: import mxnet
  from mxnet import gluon
label_desc: Use image node_id 2 for calling a global function with example usage: gcn_reduce(node) and returns: dict