def convert_ldm_unet_checkpoint(checkpoint, config, path=None, extract_ema=False):
    """
    Takes a state dict and a config, and returns a converted checkpoint.
    """

    # extract state_dict for UNet
    unet_state_dict = {}
    keys = list(checkpoint.keys())

    unet_key = "model.diffusion_model."

    # at least a 100 parameters have to start with `model_ema` in order for the checkpoint to be EMA
    if sum(k.startswith("model_ema") for k in keys) > 100 and extract_ema:
        print(f"Checkpoint {path} has both EMA and non-EMA weights.")
        print(
            "In this conversion only the EMA weights are extracted. If you want to instead extract the non-EMA"
            " weights (useful to continue fine-tuning), please make sure to remove the `--extract_ema` flag."
        )
        for key in keys:
            if key.startswith("model.diffusion_model"):
                flat_ema_key = "model_ema." + "".join(key.split(".")[1:])
                unet_state_dict[key.replace(unet_key, "")] = checkpoint.pop(flat_ema_key)
    else:
        if sum(k.startswith("model_ema") for k in keys) > 100:
            print(
                "In this conversion only the non-EMA weights are extracted. If you want to instead extract the EMA"
                " weights (usually better for inference), please make sure to add the `--extract_ema` flag."
            )

        for key in keys:
            unet_state_dict[key.replace(unet_key, "")] = checkpoint.pop(key)

    new_checkpoint = {}

    new_checkpoint["time_embedding.linear_1.weight"] = unet_state_dict["time_embed.0.weight"]
    new_checkpoint["time_embedding.linear_1.bias"] = unet_state_dict["time_embed.0.bias"]
    new_checkpoint["time_embedding.linear_2.weight"] = unet_state_dict["time_embed.2.weight"]
    new_checkpoint["time_embedding.linear_2.bias"] = unet_state_dict["time_embed.2.bias"]

    additional_embedding_substrings = [
        "local_image_concat",
        "context_embedding",
        "local_image_embedding",
        "fps_embedding",
    ]
    for k in unet_state_dict:
        if any(substring in k for substring in additional_embedding_substrings):
            diffusers_key = k.replace("local_image_concat", "image_latents_proj_in").replace(
                "local_image_embedding", "image_latents_context_embedding"
            )
            new_checkpoint[diffusers_key] = unet_state_dict[k]

    # temporal encoder.
    new_checkpoint["image_latents_temporal_encoder.norm1.weight"] = unet_state_dict[
        "local_temporal_encoder.layers.0.0.norm.weight"
    ]
    new_checkpoint["image_latents_temporal_encoder.norm1.bias"] = unet_state_dict[
        "local_temporal_encoder.layers.0.0.norm.bias"
    ]

    # attention
    qkv = unet_state_dict["local_temporal_encoder.layers.0.0.fn.to_qkv.weight"]
    q, k, v = torch.chunk(qkv, 3, dim=0)
    new_checkpoint["image_latents_temporal_encoder.attn1.to_q.weight"] = q
    new_checkpoint["image_latents_temporal_encoder.attn1.to_k.weight"] = k
    new_checkpoint["image_latents_temporal_encoder.attn1.to_v.weight"] = v
    new_checkpoint["image_latents_temporal_encoder.attn1.to_out.0.weight"] = unet_state_dict[
        "local_temporal_encoder.layers.0.0.fn.to_out.0.weight"
    ]
    new_checkpoint["image_latents_temporal_encoder.attn1.to_out.0.bias"] = unet_state_dict[
        "local_temporal_encoder.layers.0.0.fn.to_out.0.bias"
    ]

    # feedforward
    new_checkpoint["image_latents_temporal_encoder.ff.net.0.proj.weight"] = unet_state_dict[
        "local_temporal_encoder.layers.0.1.net.0.0.weight"
    ]
    new_checkpoint["image_latents_temporal_encoder.ff.net.0.proj.bias"] = unet_state_dict[
        "local_temporal_encoder.layers.0.1.net.0.0.bias"
    ]
    new_checkpoint["image_latents_temporal_encoder.ff.net.2.weight"] = unet_state_dict[
        "local_temporal_encoder.layers.0.1.net.2.weight"
    ]
    new_checkpoint["image_latents_temporal_encoder.ff.net.2.bias"] = unet_state_dict[
        "local_temporal_encoder.layers.0.1.net.2.bias"
    ]

    if "class_embed_type" in config:
        if config["class_embed_type"] is None:
            # No parameters to port
            ...
        elif config["class_embed_type"] == "timestep" or config["class_embed_type"] == "projection":
            new_checkpoint["class_embedding.linear_1.weight"] = unet_state_dict["label_emb.0.0.weight"]
            new_checkpoint["class_embedding.linear_1.bias"] = unet_state_dict["label_emb.0.0.bias"]
            new_checkpoint["class_embedding.linear_2.weight"] = unet_state_dict["label_emb.0.2.weight"]
            new_checkpoint["class_embedding.linear_2.bias"] = unet_state_dict["label_emb.0.2.bias"]
        else:
            raise NotImplementedError(f"Not implemented `class_embed_type`: {config['class_embed_type']}")

    new_checkpoint["conv_in.weight"] = unet_state_dict["input_blocks.0.0.weight"]
    new_checkpoint["conv_in.bias"] = unet_state_dict["input_blocks.0.0.bias"]

    first_temp_attention = [v for v in unet_state_dict if v.startswith("input_blocks.0.1")]
    paths = renew_attention_paths(first_temp_attention)
    meta_path = {"old": "input_blocks.0.1", "new": "transformer_in"}
    assign_to_checkpoint(paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config)

    new_checkpoint["conv_norm_out.weight"] = unet_state_dict["out.0.weight"]
    new_checkpoint["conv_norm_out.bias"] = unet_state_dict["out.0.bias"]
    new_checkpoint["conv_out.weight"] = unet_state_dict["out.2.weight"]
    new_checkpoint["conv_out.bias"] = unet_state_dict["out.2.bias"]

    # Retrieves the keys for the input blocks only
    num_input_blocks = len({".".join(layer.split(".")[:2]) for layer in unet_state_dict if "input_blocks" in layer})
    input_blocks = {
        layer_id: [key for key in unet_state_dict if f"input_blocks.{layer_id}" in key]
        for layer_id in range(num_input_blocks)
    }

    # Retrieves the keys for the middle blocks only
    num_middle_blocks = len({".".join(layer.split(".")[:2]) for layer in unet_state_dict if "middle_block" in layer})
    middle_blocks = {
        layer_id: [key for key in unet_state_dict if f"middle_block.{layer_id}" in key]
        for layer_id in range(num_middle_blocks)
    }

    # Retrieves the keys for the output blocks only
    num_output_blocks = len({".".join(layer.split(".")[:2]) for layer in unet_state_dict if "output_blocks" in layer})
    output_blocks = {
        layer_id: [key for key in unet_state_dict if f"output_blocks.{layer_id}" in key]
        for layer_id in range(num_output_blocks)
    }

    for i in range(1, num_input_blocks):
        block_id = (i - 1) // (config["layers_per_block"] + 1)
        layer_in_block_id = (i - 1) % (config["layers_per_block"] + 1)

        resnets = [
            key for key in input_blocks[i] if f"input_blocks.{i}.0" in key and f"input_blocks.{i}.0.op" not in key
        ]
        attentions = [key for key in input_blocks[i] if f"input_blocks.{i}.1" in key]
        temp_attentions = [key for key in input_blocks[i] if f"input_blocks.{i}.2" in key]

        if f"input_blocks.{i}.op.weight" in unet_state_dict:
            new_checkpoint[f"down_blocks.{block_id}.downsamplers.0.conv.weight"] = unet_state_dict.pop(
                f"input_blocks.{i}.op.weight"
            )
            new_checkpoint[f"down_blocks.{block_id}.downsamplers.0.conv.bias"] = unet_state_dict.pop(
                f"input_blocks.{i}.op.bias"
            )

        paths = renew_resnet_paths(resnets)
        meta_path = {"old": f"input_blocks.{i}.0", "new": f"down_blocks.{block_id}.resnets.{layer_in_block_id}"}
        assign_to_checkpoint(
            paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
        )

        temporal_convs = [key for key in resnets if "temopral_conv" in key]
        paths = renew_temp_conv_paths(temporal_convs)
        meta_path = {
            "old": f"input_blocks.{i}.0.temopral_conv",
            "new": f"down_blocks.{block_id}.temp_convs.{layer_in_block_id}",
        }
        assign_to_checkpoint(
            paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
        )

        if len(attentions):
            paths = renew_attention_paths(attentions)
            meta_path = {"old": f"input_blocks.{i}.1", "new": f"down_blocks.{block_id}.attentions.{layer_in_block_id}"}
            assign_to_checkpoint(
                paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
            )

        if len(temp_attentions):
            paths = renew_attention_paths(temp_attentions)
            meta_path = {
                "old": f"input_blocks.{i}.2",
                "new": f"down_blocks.{block_id}.temp_attentions.{layer_in_block_id}",
            }
            assign_to_checkpoint(
                paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
            )

    resnet_0 = middle_blocks[0]
    temporal_convs_0 = [key for key in resnet_0 if "temopral_conv" in key]
    attentions = middle_blocks[1]
    temp_attentions = middle_blocks[2]
    resnet_1 = middle_blocks[3]
    temporal_convs_1 = [key for key in resnet_1 if "temopral_conv" in key]

    resnet_0_paths = renew_resnet_paths(resnet_0)
    meta_path = {"old": "middle_block.0", "new": "mid_block.resnets.0"}
    assign_to_checkpoint(
        resnet_0_paths, new_checkpoint, unet_state_dict, config=config, additional_replacements=[meta_path]
    )

    temp_conv_0_paths = renew_temp_conv_paths(temporal_convs_0)
    meta_path = {"old": "middle_block.0.temopral_conv", "new": "mid_block.temp_convs.0"}
    assign_to_checkpoint(
        temp_conv_0_paths, new_checkpoint, unet_state_dict, config=config, additional_replacements=[meta_path]
    )

    resnet_1_paths = renew_resnet_paths(resnet_1)
    meta_path = {"old": "middle_block.3", "new": "mid_block.resnets.1"}
    assign_to_checkpoint(
        resnet_1_paths, new_checkpoint, unet_state_dict, config=config, additional_replacements=[meta_path]
    )

    temp_conv_1_paths = renew_temp_conv_paths(temporal_convs_1)
    meta_path = {"old": "middle_block.3.temopral_conv", "new": "mid_block.temp_convs.1"}
    assign_to_checkpoint(
        temp_conv_1_paths, new_checkpoint, unet_state_dict, config=config, additional_replacements=[meta_path]
    )

    attentions_paths = renew_attention_paths(attentions)
    meta_path = {"old": "middle_block.1", "new": "mid_block.attentions.0"}
    assign_to_checkpoint(
        attentions_paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
    )

    temp_attentions_paths = renew_attention_paths(temp_attentions)
    meta_path = {"old": "middle_block.2", "new": "mid_block.temp_attentions.0"}
    assign_to_checkpoint(
        temp_attentions_paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
    )

    for i in range(num_output_blocks):
        block_id = i // (config["layers_per_block"] + 1)
        layer_in_block_id = i % (config["layers_per_block"] + 1)
        output_block_layers = [shave_segments(name, 2) for name in output_blocks[i]]
        output_block_list = {}

        for layer in output_block_layers:
            layer_id, layer_name = layer.split(".")[0], shave_segments(layer, 1)
            if layer_id in output_block_list:
                output_block_list[layer_id].append(layer_name)
            else:
                output_block_list[layer_id] = [layer_name]

        if len(output_block_list) > 1:
            resnets = [key for key in output_blocks[i] if f"output_blocks.{i}.0" in key]
            attentions = [key for key in output_blocks[i] if f"output_blocks.{i}.1" in key]
            temp_attentions = [key for key in output_blocks[i] if f"output_blocks.{i}.2" in key]

            resnet_0_paths = renew_resnet_paths(resnets)
            paths = renew_resnet_paths(resnets)

            meta_path = {"old": f"output_blocks.{i}.0", "new": f"up_blocks.{block_id}.resnets.{layer_in_block_id}"}
            assign_to_checkpoint(
                paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
            )

            temporal_convs = [key for key in resnets if "temopral_conv" in key]
            paths = renew_temp_conv_paths(temporal_convs)
            meta_path = {
                "old": f"output_blocks.{i}.0.temopral_conv",
                "new": f"up_blocks.{block_id}.temp_convs.{layer_in_block_id}",
            }
            assign_to_checkpoint(
                paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
            )

            output_block_list = {k: sorted(v) for k, v in output_block_list.items()}
            if ["conv.bias", "conv.weight"] in output_block_list.values():
                index = list(output_block_list.values()).index(["conv.bias", "conv.weight"])
                new_checkpoint[f"up_blocks.{block_id}.upsamplers.0.conv.weight"] = unet_state_dict[
                    f"output_blocks.{i}.{index}.conv.weight"
                ]
                new_checkpoint[f"up_blocks.{block_id}.upsamplers.0.conv.bias"] = unet_state_dict[
                    f"output_blocks.{i}.{index}.conv.bias"
                ]

                # Clear attentions as they have been attributed above.
                if len(attentions) == 2:
                    attentions = []

            if len(attentions):
                paths = renew_attention_paths(attentions)
                meta_path = {
                    "old": f"output_blocks.{i}.1",
                    "new": f"up_blocks.{block_id}.attentions.{layer_in_block_id}",
                }
                assign_to_checkpoint(
                    paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
                )

            if len(temp_attentions):
                paths = renew_attention_paths(temp_attentions)
                meta_path = {
                    "old": f"output_blocks.{i}.2",
                    "new": f"up_blocks.{block_id}.temp_attentions.{layer_in_block_id}",
                }
                assign_to_checkpoint(
                    paths, new_checkpoint, unet_state_dict, additional_replacements=[meta_path], config=config
                )
        else:
            resnet_0_paths = renew_resnet_paths(output_block_layers, n_shave_prefix_segments=1)
            for path in resnet_0_paths:
                old_path = ".".join(["output_blocks", str(i), path["old"]])
                new_path = ".".join(["up_blocks", str(block_id), "resnets", str(layer_in_block_id), path["new"]])
                new_checkpoint[new_path] = unet_state_dict[old_path]

            temopral_conv_paths = [l for l in output_block_layers if "temopral_conv" in l]
            for path in temopral_conv_paths:
                pruned_path = path.split("temopral_conv.")[-1]
                old_path = ".".join(["output_blocks", str(i), str(block_id), "temopral_conv", pruned_path])
                new_path = ".".join(["up_blocks", str(block_id), "temp_convs", str(layer_in_block_id), pruned_path])
                new_checkpoint[new_path] = unet_state_dict[old_path]

    return new_checkpoint

    Takes a state dict and a config, and returns a converted checkpoint.
    
scripts/convert_i2vgen_to_diffusers.py