human
Solve the following python programming problem given the following code:
def testExactPreferredToWildcards(self) : 
    class MetadataTestNodeD (Gaffer.Node) : 
        def __init__(self, name = 'MetadataTestNodeD') : 
            Gaffer.Node.__init__ (self, name) 
            self ['a'] = Gaffer.IntPlug () 
            self ['b'] = Gaffer.IntPlug () 
IECore.registerRunTimeTyped (MetadataTestNodeD) 
    Gaffer.Metadata.registerNode (MetadataTestNodeD, plugs = { 
        '*' : ['test', 'wildcard'], 
        'a' : ['test', 'exact'], 
}) 
    n = MetadataTestNodeD () 
    self.assertEqual (Gaffer.Metadata.plugValue (n ['a'], 'test'), 'exact') 
    self.assertEqual (Gaffer.Metadata.plugValue (self ['b'], 'test'), 'wildcard') 

    
    

    Fix the buggy line: self.assertEqual (Gaffer.Metadata.plugValue (self ['b'], 'test'), 'wildcard')
assistant
#Here is Python code to fix the buggy line: self.

self.assertEqual (Gaffer.Metadata.plugValue (n ['b'], 'test'), 'wildcard')