code: def testIndependentVertexSets(self):
      tests = {
          (4, -1): [],
          (2, 2): [(0, 3), (0, 4), (1, 2), (2, 3), (2, 4), (3, 4)],
          (-1, -1): [
              (0,),
              (1,),
              (2,),
              (3,),
              (4,),
              (0, 3),
              (0, 4),
              (1, 2),
              (2, 3),
              (2, 4),
              (3, 4),
              (0, 3, 4),
              (2, 3, 4),
          ],
      }
      for (lo, hi), exp in tests.items():
          self.assertEqual(exp, self.g1.independent_vertex_sets(lo, hi))
  
imports: import unittest
  from igraph import Graph
  from .utils import temporary_file
label_desc: Use image node_id 2 for calling the IndependentVertexSetTests obj's underlying member method code with example usage: obj.testIndependentVertexSets() without return types