human
Solve the following python programming problem given the following code:
def testUndoOfPersistentInstanceValues(self) : 
    s = Gaffer.ScriptNode () 
    s ['n'] = GafferTest.AddNode () 
    def assertNonExistent() : 
        self.assertEqual (Gaffer.Metadata.nodeValue (s ['n'], 'a'), None) 
        self.assertEqual (Gaffer.Metadata.plugValue (s ['n'] ['op1'], 'b'), None) 
def assertPersistent() : 
        self.assertEqual (Gaffer.Metadata.registeredNodeValues (s ['n'], instanceOnly = True), ['a']) 
        self.assertEqual (Gaffer.Metadata.registeredPlugValues (s ['n'] ['op1'], instanceOnly = True), ['b']) 
        self.assertEqual (Gaffer.Metadata.registeredNodeValues (s ['n'], instanceOnly = True, persistentOnly = True), ['a']) 
        self.assertEqual (Gaffer.Metadata.registeredPlugValues (s ['n'] ['op1'], instanceOnly = True, persistentOnly = True), ['b']) 
        self.assertEqual (Gaffer.Metadata.nodeValue (s ['n'], 'a'), 1) 
        self.assertEqual (Gaffer.Metadata.plugValue (s ['n'] ['op1'], 'b'), 2) 
def assertNonPersistent() : 
        self.assertEqual (Gaffer.Metadata.registeredNodeValues (s ['n'], instanceOnly = True), ['a']) 
        self.assertEqual (Gaffer.Metadata.registeredPlugValues (s ['n'] ['op1'], instanceOnly = True), ['b']) 
        self.assertEqual (Gaffer.Metadata.registeredNodeValues (s ['n'], instanceOnly = True, persistentOnly = True), []) 
        self.assertEqual (Gaffer.Metadata.registeredPlugValues (s ['n'] ['op1'], instanceOnly = True, persistentOnly = True), []) 
        self.assertEqual (Gaffer.Metadata.nodeValue (s ['n'], 'a'), 1) 
        self.assertEqual (Gaffer.Metadata.plugValue (s ['n'] ['op1'], 'b'), 2) 
assertNonExistent () 
    with Gaffer.UndoContext (s) : 
        Gaffer.Metadata.registerNodeValue (self ['n'], 'a', 1, persistent = True) 
        Gaffer.Metadata.registerPlugValue (s ['n'] ['op1'], 'b', 2, persistent = True) 
assertPersistent () 
    with Gaffer.UndoContext (s) : 
        Gaffer.Metadata.registerNodeValue (s ['n'], 'a', 1, persistent = False) 
        Gaffer.Metadata.registerPlugValue (s ['n'] ['op1'], 'b', 2,...

    
    

    Fix the buggy line: Gaffer.Metadata.registerNodeValue (self ['n'], 'a', 1, persistent = True)
assistant
#Here is Python program to fix the buggy line: Gaffer.

Gaffer.Metadata.registerNodeValue (s ['n'], 'a', 1, persistent = True)