code: def testPyMethods(self):
      inull = MPI.INFO_NULL
  
      def getitem():
          return inull["k"]
  
      def setitem():
          inull["k"] = "v"
  
      def delitem():
          del inull["k"]
  
      def update():
          inull.update([])
  
      def pop():
          inull.pop("k")
  
      def popitem():
          inull.popitem()
  
      self.assertEqual(len(inull), 0)
      self.assertNotIn("key", inull)
      self.assertRaises(KeyError, getitem)
      self.assertRaises(KeyError, setitem)
      self.assertRaises(KeyError, delitem)
      self.assertRaises(KeyError, update)
      self.assertRaises(KeyError, pop)
      self.assertRaises(KeyError, popitem)
      self.assertIsNone(inull.get("key", None))
      self.assertIsNone(inull.pop("key", None))
      self.assertEqual(inull.keys(), [])
      self.assertEqual(inull.values(), [])
      self.assertEqual(inull.items(), [])
      self.assertEqual(inull.copy(), inull)
      inull.clear()
  
imports: from mpi4py import MPI
  import mpiunittest
  import sys
label_desc: Use image node_id 3 for calling the TestInfoNull obj's underlying member method code with example usage: obj.testPyMethods() and returns: inull