def key_release_event(self, widget, event):
        """
        Called when a key is released after being pressed.
        Adjust method signature as appropriate for callback.
        """
        # get keyname or keycode and translate to ginga standard
        # keyname =
        # keycode =
        keyname = ''  # self.transkey(keyname, keycode)
        self.logger.debug("key release event, key=%s" % (keyname))
        return self.make_ui_callback('key-release', keyname)
Called when a key is released after being pressed.
        Adjust method signature as appropriate for callback.