def scale_action(action_space, action):
    """
    Rescale the action from [low, high] to [-1, 1]
    (no need for symmetric action space)

    :param action_space: (gym.spaces.box.Box)
    :param action: (np.ndarray)
    :return: (np.ndarray)
    """
    low, high = action_space.low, action_space.high
    return 2.0 * ((action - low) / (high - low)) - 1.0
