def copy_metadata(nb_data):
    """Copy metadata of notebook
    
    Args:
        nb_data (JSON): a json data load from jupyter notebook

    Returns:
        dict: metadate copied from nb_data
    """
    metadata = dict()
    metadata["metadata"] = nb_data["metadata"]
    metadata["nbformat"] = nb_data["nbformat"]
    metadata["nbformat_minor"] = nb_data["nbformat_minor"]
    return metadata