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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 on_selection_changed(self, sel):
 """The user changed selection"""

        m, self.editing_iter = sel.get_selected()

        if self.editing_iter:
            self.editing_model = m[self.editing_iter][0]
            self.show_curr_model_view(self.editing_model, False)
            
        else: self.view.remove_currency_view()
            
        return