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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_changed(self):
 """ Update the tree items """

        self._updating = True
        to_collapse = []
        self.clear()
        if self._editor and self._outline_mode and self._folding_panel:
            items, to_collapse = self.to_tree_widget_items(
                self._outline_mode.definitions, to_collapse=to_collapse)
            if len(items):
                self.addTopLevelItems(items)
                self.expandAll()
                for item in reversed(to_collapse):
                    self.collapseItem(item)
                self._updating = False
                return

        # no data
        root = QtWidgets.QTreeWidgetItem()
        root.setText(0, _('No data'))
        root.setIcon(0, icons.icon(
            'dialog-information', ':/pyqode-icons/rc/dialog-info.png',
            'fa.info-circle'))
        self.addTopLevelItem(root)
        self._updating = False
        self.sync()