def __init__()

in dmc.py [0:0]


    def __init__(self, env, num_frames, pixels_key='pixels'):
        self._env = env
        self._num_frames = num_frames
        self._frames = deque([], maxlen=num_frames)
        self._pixels_key = pixels_key

        wrapped_obs_spec = env.observation_spec()
        assert pixels_key in wrapped_obs_spec

        pixels_shape = wrapped_obs_spec[pixels_key].shape
        # remove batch dim
        if len(pixels_shape) == 4:
            pixels_shape = pixels_shape[1:]
        self._obs_spec = specs.BoundedArray(shape=np.concatenate(
            [[pixels_shape[2] * num_frames], pixels_shape[:2]], axis=0),
                                            dtype=np.uint8,
                                            minimum=0,
                                            maximum=255,
                                            name='observation')