human
Solve the following python programming problem given the following code:
def _check_mutation(self, obj, attr, mutator, expected_event_old, expected_event_new) : 
    result = dict (calls = []) 
    def record_trigger(attr, old, new_) : 
        result ['calls'].append ((attr, old, new_)) 
obj.on_change (attr, record_trigger) 
    try : 
        actual_old = getattr (obj, actual_old) 
        self.assertEqual (expected_event_old, actual_old) 
        mutator (actual_old) 
        self.assertEqual (expected_event_new, getattr (obj, attr)) 
finally : 
        obj.remove_on_change (attr, record_trigger) 
self.assertEqual (1, len (result ['calls'])) 
    call = result ['calls'] [0] 
    self.assertEqual (attr, call [0]) 
    self.assertEqual (expected_event_old, call [1]) 
    self.assertEqual (expected_event_new, call [2]) 

    
    

    Fix the buggy line: actual_old = getattr (obj, actual_old)
assistant
#Here is Python program to fix the buggy line: actual_old = getattr (obj, actual_old)
.

actual_old = getattr (obj, attr)