docs: def set_ds9(self, level="PREF"):
          """
          Set the default values on the ds9 display.
          """
          self.set_zoom()
          ds9_settings = config.read("DS9."+level)
          for key in ds9_settings.keys():
              value = ds9_settings[key]
              cmd = key.replace("_", " ")
              self.ds9.set("{} {}".format(cmd, value))