def __init__(self, env):
        """No stacking. Trajectory View API takes care of this."""
        gym.Wrapper.__init__(self, env)
        shp = env.observation_space.shape
        assert shp[2] == 1
        self.observation_space = spaces.Box(
            low=0, high=255, shape=(shp[0], shp[1]), dtype=env.observation_space.dtype
        )