def METHOD_NAME(filepath: str):
    """Open and unmarshal the _index.json file
    :param filepath: Path to the JSON file
    :return: Dict representing index file contents
    """
    if filepath is None:
        raise ContextLoaderError("_index.json file was not selected")
    try:
        with open(filepath, "rb") as _file:
            return json.load(_file)
    except Exception as ex:
        raise ContextLoaderError(
            "Failed to parse json file {}".format(filepath)
        ) from ex