<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_archiver_index(config, archiver):
 """ Get the contents of the archiver index file. :param config: The configuration :type config: :class:`wily.config.WilyConfig` :param archiver: The name of the archiver type (e.g. 'git') :type archiver: ``str`` :return: The index data :rtype: ``dict`` """

    root = pathlib.Path(config.cache_path) / archiver
    with (root / "index.json").open("r") as index_f:
        index = json.load(index_f)
    return index