code: def testDisjointUnion(self):
      g1 = Graph.Tree(7, 2)
      g2 = Graph.Lattice([7])
  
      # Method
      g = g1.disjoint_union(g2)
      self.assertTrue(g.vcount() == 14 and g.ecount() == 13)
  
      # Module function
      g = disjoint_union([g1, g2])
      self.assertTrue(g.vcount() == 14 and g.ecount() == 13)
  
imports: import unittest
  from igraph import Graph, disjoint_union, intersection, union
label_desc: Use image node_id 5 for calling the OperatorTests obj's underlying member method code with example usage: obj.testDisjointUnion() without return types