<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def update(self, item):
 """Manually update an item's display in the list :param item: The item to be updated. """

        self.model.set(self._iter_for(item), 0, item)