code: def testUnionMany(self):
      gs = [Graph.Tree(7, 2), Graph.Lattice([7]), Graph.Lattice([7])]
      g = union(gs)
      self.assertTrue(g.vcount() == 7 and g.ecount() == 12)
  
imports: import unittest
  from igraph import Graph, disjoint_union, intersection, union
label_desc: Use image node_id 13 for calling the OperatorTests obj's underlying member method code with example usage: obj.testUnionMany() without return types