def list_downloaded(root=None, **kwargs):
    """
    .. versionadded:: 3000?

    List prefetched packages downloaded by apt in the local disk.

    root
        operate on a different root directory.

    CLI Example:

    .. code-block:: bash

        salt '*' pkg.list_downloaded
    """
    CACHE_DIR = "/var/cache/apt"
    if root:
        CACHE_DIR = os.path.join(root, os.path.relpath(CACHE_DIR, os.path.sep))

    ret = {}
    for root, dirnames, filenames in salt.utils.path.os_walk(CACHE_DIR):
        for filename in fnmatch.filter(filenames, "*.deb"):
            package_path = os.path.join(root, filename)
            pkg_info = __salt__["lowpkg.bin_pkg_info"](package_path)
            pkg_timestamp = int(os.path.getctime(package_path))
            ret.setdefault(pkg_info["name"], {})[pkg_info["version"]] = {
                "path": package_path,
                "size": os.path.getsize(package_path),
                "creation_date_time_t": pkg_timestamp,
                "creation_date_time": datetime.datetime.utcfromtimestamp(
                    pkg_timestamp
                ).isoformat(),
            }
    return ret