<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _updateTabStopWidth(self):
 """Update tabstop width after font or indentation changed """

        self.setTabStopWidth(self.fontMetrics().width(' ' * self._indenter.width))