code: def testDifference(self):
      g = Graph.Tree(7, 2) - Graph.Lattice([7])
      self.assertTrue(g.vcount() == 7 and g.ecount() == 5)
      self.assertTrue(
          sorted(g.get_edgelist())
          == [(0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]
      )
  
imports: import unittest
  from igraph import Graph, disjoint_union, intersection, union
label_desc: Use image node_id 3 for calling the OperatorTests obj's underlying member method code with example usage: obj.testDifference() without return types