<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_timescale(self, timescale):
 """ Add a time scale to the plot. :param timescale: the timescale to be added :type timescale: :class:`~aeneas.plotter.PlotTimeScale` :raises: TypeError: if ``timescale`` is not an instance of :class:`~aeneas.plotter.PlotTimeScale` """

        if not isinstance(timescale, PlotTimeScale):
            self.log_exc(u"timescale must be an instance of PlotTimeScale", None, True, TypeError)
        self.timescale = timescale
        self.log(u"Added timescale")