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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def sort_top_level_items(self, key):

 """Sorting tree wrt top level items"""

        self.save_expanded_state()
        items = sorted([self.takeTopLevelItem(0)
                        for index in range(self.topLevelItemCount())], key=key)
        for index, item in enumerate(items):
            self.insertTopLevelItem(index, item)
        self.restore_expanded_state()