human
Solve the following python programming problem given the following code:
@ mock.patch ('bareon.utils.grub.os.path.isfile') 
def test_guess_grub(self, mock_isfile) : 
    side_effect_values = { 
        '/target/sbin/grub' : True, 
        '/target/usr/sbin/grub' : False, 
} 
    def side_effect(key) : 
        return side_effect_values [key] 
mock_isfile.side_effect = side_effect_values 
    self.assertEqual (gu.guess_grub ('/target'), '/sbin/grub') 
    side_effect_values = { 
        '/target/sbin/grub' : False, 
        '/target/usr/sbin/grub' : True, 
} 
    self.assertEqual (gu.guess_grub ('/target'), '/usr/sbin/grub') 
    side_effect_values = { 
        '/target/sbin/grub' : False, 
        '/target/usr/sbin/grub' : False, 
} 
    self.assertRaises (errors.GrubUtilsError, gu.guess_grub, '/target') 

    
    

    Fix the buggy line: mock_isfile.side_effect = side_effect_values
assistant
#Here is Python program to fix the buggy line: mock_isfile.

mock_isfile.side_effect = side_effect