def __init__(self, env, skip=4):
        """Return only every `skip`-th frame"""
        gym.Wrapper.__init__(self, env)
        # most recent raw observations (for max pooling across time steps)
        self._obs_buffer = np.zeros((2,)+env.observation_space.shape, dtype='uint8')
        self._skip       = skip
Return only every `skip`-th frame
surreal/env/atari_wrappers.py