I wonder why the action string of a clicking operation ```click [25]``` is formatted like this: ```click [25] where [25]```? Why not simply ```click [25]```? Thanks. https://github.com/web-arena-x/visualwebarena/blob/89f5af29305c3d1e9f97ce4421462060a70c9a03/browser_env/actions.py#L170