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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def get_checkpoints_for_actor(actor_id):
 """Get the available checkpoints for the given actor ID, return a list sorted by checkpoint timestamp in descending order. """

    checkpoint_info = ray.worker.global_state.actor_checkpoint_info(actor_id)
    if checkpoint_info is None:
        return []
    checkpoints = [
        Checkpoint(checkpoint_id, timestamp) for checkpoint_id, timestamp in
        zip(checkpoint_info["CheckpointIds"], checkpoint_info["Timestamps"])
    ]
    return sorted(
        checkpoints,
        key=lambda checkpoint: checkpoint.timestamp,
        reverse=True,
    )