code: def testIndependenceNumber(self):
      self.assertEqual(self.g2.independence_number(), 6)
      self.assertEqual(self.g2.alpha(), 6)
  
imports: import unittest
  from igraph import Graph
  from .utils import temporary_file
label_desc: Use image node_id 5 for calling the IndependentVertexSetTests obj's underlying member method code with example usage: obj.testIndependenceNumber() without return types