code: def mfunc(edges):
      return {"m": edges.src["x"]}
  
file_path: dgl/tests/python/common/test_propagate.py
imports: import unittest
  import backend
  import dgl
  import networkx
  from utils import check_fail, parametrize_idtype
label_desc: Use image node_id 2 for calling a global function with example usage: mfunc(edges) and returns: dict