[content] sample.py (python)
    jax.distributed.initialize()

    rng = jax.random.key(args.seed)

    # --- Load Genie checkpoint ---
    rngs = nnx.Rngs(rng)
    genie = Genie(
        # Tokenizer
        in_dim=args.image_channels,
        tokenizer_dim=args.tokenizer_dim,
        tokenizer_ffn_dim=args.tokenizer_ffn_dim,
        latent_patch_dim=args.latent_patch_dim,
        num_patch_latents=args.num_patch_latents,
        patch_size=args.patch_size,
        tokenizer_num_blocks=args.tokenizer_num_blocks,
        tokenizer_num_heads=args.tokenizer_num_heads,
        # LAM
        lam_dim=args.lam_dim,
        lam_ffn_dim=args.lam_ffn_dim,
        latent_action_dim=args.latent_action_dim,
        num_latent_actions=args.num_latent_actions,
        lam_patch_size=args.lam_patch_size,
        lam_num_blocks=args.lam_num_blocks,
        lam_num_heads=args.lam_num_heads,
        lam_co_train=False,
        # Dynamics
        dyna_dim=args.dyna_dim,
        dyna_ffn_dim=args.dyna_ffn_dim,
        dyna_num_blocks=args.dyna_num_blocks,
        dyna_num_heads=args.dyna_num_heads,
        param_dtype=args.param_dtype,
        dtype=args.dtype,
        use_flash_attention=args.use_flash_attention,
        rngs=rngs,
    )

    handler_registry = ocp.handlers.DefaultCheckpointHandlerRegistry()
    handler_registry.add(
        "model_state", ocp.args.PyTreeSave, ocp.handlers.PyTreeCheckpointHandler
    )
    handler_registry.add(
        "model_state", ocp.args.PyTreeRestore, ocp.handlers.PyTreeCheckpointHandler
    )
    checkpoint_options = ocp.CheckpointManagerOptions(
        step_format_fixed_length=6,
    )
    checkpoint_manager = ocp.CheckpointManager(
        args.checkpoint,
        options=checkpoint_options,
        handler_registry=handler_registry,
    )

    dummy_tx = optax.adamw(
        learning_rate=optax.linear_schedule(0.0001, 0.0001, 10000),
        b1=0.9,
        b2=0.9,
        weight_decay=1e-4,
        mu_dtype=args.dtype,
    )
    dummy_optimizer = nnx.Optimizer(genie, dummy_tx)

    abstract_optimizer = nnx.eval_shape(lambda: dummy_optimizer)
    abstract_optimizer_state = nnx.state(abstract_optimizer)
    restored = checkpoint_manager.restore(
        checkpoint_manager.latest_step(),
        args=ocp.args.Composite(
            model_state=ocp.args.PyTreeRestore(abstract_optimizer_state),  # type: ignore
        ),
    )
    restored_optimizer_state = restored["model_state"]
    nnx.update(dummy_optimizer, restored_optimizer_state)

    # --- Define sampling function ---
    def _sampling_fn(model: Genie, batch: dict) -> jax.Array:
        """Runs Genie.sample with pre-defined generation hyper-parameters."""
        return model.sample(
            batch,
            args.seq_len,
            args.maskgit_steps,
            args.temperature,
            args.sample_argmax,
        )

    # --- Define autoregressive sampling loop ---
    @nnx.jit
    def _autoreg_sample(rng, video_batch, action_batch):
        vid = video_batch[:, : args.start_frame + 1]
        rng, _rng = jax.random.split(rng)
        batch = dict(videos=vid, latent_actions=action_batch, rng=_rng)
        generated_vid = _sampling_fn(genie, batch)
        return generated_vid

    # --- Get video + latent actions ---
    array_record_files = [
        os.path.join(args.data_dir, x)
        for x in os.listdir(args.data_dir)
        if x.endswith(".array_record")
    ]
    dataloader = get_dataloader(
        array_record_files,
        args.seq_len,
        args.batch_size,
        args.image_height,
        args.image_width,
        args.image_channels,
        # We don't use workers in order to avoid grain shutdown issues (https://github.com/google/grain/issues/398)
        num_workers=0,
        prefetch_buffer_size=1,
        seed=args.seed,
    )
    dataloader = iter(dataloader)
    video_batch = next(dataloader)
    video_batch = video_batch.astype(args.dtype) / 255.0
    # Get latent actions for all videos in the batch
    batch = dict(videos=video_batch)
    action_batch = genie.vq_encode(batch, training=False)

    # --- Sample + evaluate video ---
    vid = _autoreg_sample(rng, video_batch, action_batch)
    gt = video_batch[:, : vid.shape[1]].clip(0, 1).reshape(-1, *video_batch.shape[2:])
    recon = vid.clip(0, 1).reshape(-1, *vid.shape[2:])
    ssim = jnp.asarray(
        pix.ssim(gt[:, args.start_frame + 1 :], recon[:, args.start_frame + 1 :])
    ).mean()
    print(f"SSIM: {ssim}")

    # --- Construct video ---
    true_videos = (video_batch * 255).astype(np.uint8)
    pred_videos = (vid * 255).astype(np.uint8)
    video_comparison = np.zeros((2, *vid.shape), dtype=np.uint8)
    video_comparison[0] = true_videos[:, : args.seq_len]
    video_comparison[1] = pred_videos
    frames = einops.rearrange(video_comparison, "n b t h w c -> t (b h) (n w) c")

    # --- Save video ---
    imgs = [Image.fromarray(img) for img in frames]
    # Write actions on each frame, on each row (i.e., for each video in the batch, on the GT row)
    for t, img in enumerate(imgs[1:]):
        d = ImageDraw.Draw(img)
        for row in range(action_batch.shape[0]):
            action = action_batch[row, t, 0]
            y_offset = row * video_batch.shape[2] + 2