def METHOD_NAME(self):
    if self._mt_objs is not None:
        all_freqs = []
        for mt_obj in self._mt_objs:
            all_freqs.extend(list(mt_obj.Z.freq))
        if self.use_period:
            all_periods = 1.0 / np.array(all_freqs)
            # self._histogram.set_data(all_periods)
            all_unique = sorted(list(set(all_periods)))
        else:
            # self._histogram.set_data(all_freqs)
            all_unique = sorted(list(set(all_freqs)))
        self._histogram.set_data(all_unique)
        self._histogram.update_figure()
        # sort all frequencies in ascending order
        for period in all_unique:
            self.ui.comboBoxPeriod.addItem("%.5f" % period)
        self.ui.comboBoxPeriod.setCurrentIndex(0)
        self.update_histogram()