unzoom display 1 level or all the way

def unzoom(self, full=False, delay_draw=False):
        """unzoom display 1 level or all the way"""
        if full:
            self.zoom_lims = self.zoom_lims[:1]
            self.zoom_lims = []
        elif len(self.zoom_lims) > 0:
            self.zoom_lims.pop()
        self.set_viewlimits()
        if not delay_draw:
            self.canvas.draw()