code: def testUnionManyEdgemap(self):
      gs = [
          Graph.Formula("A-B"),
          Graph.Formula("C-D, A-B"),
      ]
      gs[0].es[0]["attr"] = "set"
      gs[1].es[0]["attr"] = "set_too"
      g = union(gs)
      for e in g.es:
          vnames = [g.vs[e.source]["name"], g.vs[e.target]["name"]]
          if set(vnames) == {"A", "B"}:
              self.assertTrue(e["attr"] == "set")
          else:
              self.assertTrue(e["attr"] == "set_too")
  
imports: import unittest
  from igraph import Graph, disjoint_union, intersection, union
label_desc: Use image node_id 15 for calling the OperatorTests obj's underlying member method code with example usage: obj.testUnionManyEdgemap() without return types