Return a string that will show whether the string is up or down

        return 'down' if the key is a press only
        return 'up' if the key is up only
        return '' if the key is up & down (as default)

def _get_down_up_string(self):
        """Return a string that will show whether the string is up or down

        return 'down' if the key is a press only
        return 'up' if the key is up only
        return '' if the key is up & down (as default)
        """
        down_up = ""
        if not (self.down and self.up):
            if self.down:
                down_up = "down"
            elif self.up:
                down_up = "up"
        return down_up