code: def testNonzero(self):
      self.assertTrue(Graph(1))
      self.assertFalse(Graph(0))
  
imports: import unittest
  from igraph import Graph, disjoint_union, intersection, union
label_desc: Use image node_id 26 for calling the OperatorTests obj's underlying member method code with example usage: obj.testNonzero() without return types