def METHOD_NAME(self, *args):
    self.hub.broadcast(GlobalDisplayUnitChanged('spectral',
                                                self.spectral_unit.selected,
                                                sender=self))
    xunit = _valid_glue_display_unit(self.spectral_unit.selected, self.spectrum_viewer, 'x')
    if self.spectrum_viewer.state.x_display_unit != xunit:
        self.spectrum_viewer.state.x_display_unit = xunit