human
Solve the following python programming problem given the following code:
@ mock.patch.object (task.LOG, 'warn') 
def test_update_progress_upper_bound(self, mocked_warn) : 
    result = [] 
    def progress_callback(event_type, details) : 
        result.append (details.pop ('progress')) 
a_task = ProgressTask () 
    a_task.notifier.register (task.EVENT_UPDATE_PROGRESS, <MASK>) 
    a_task.execute ([1.0, 1.5, 2.0]) 
    self.assertEqual ([1.0, 1.0, 1.0], result) 
    self.assertEqual (2, mocked_warn.call_count) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def progress_callback(