<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _on_wid_changed(self, wid):
 """Called when the widget is changed"""

        if self._itsme: return
        self.update_model(self._get_idx_from_widget(wid))
        return