def upload_related(sdk, existing_asset_id, file, metadata_type=None):
    """Upload a related asset onto existing_asset_id; return the response dict."""
    return sdk.upload_related_asset(existing_asset_id, None, metadata_type, "replace", file)

export async function uploadRelated(sdk, existingAssetId, file, metadataType = null) {
    // Attach a related file (proxy/poster) to an existing asset.
    return await sdk.uploadRelatedAsset(existingAssetId, null, metadataType, "replace", file);
}