How to use the productmd.discinfo.DiscInfo function in productmd

log.debug("Checking %s", what)
        if not isys.isIsoImage(what):
            continue

        log.debug("Mounting %s on %s", what, mount_path)
        try:
            blivet.util.mount(what, mount_path, fstype="iso9660", options="ro")
        except OSError:
            continue

        if not os.access(discinfo_path, os.R_OK):
            blivet.util.umount(mount_path)
            continue

        log.debug("Reading .discinfo")
        disc_info = DiscInfo()

        # TODO replace next 2 blocks with:
        #   pyanaconda.modules.payloads.source.utils.is_valid_install_disk
        try:
            disc_info.load(discinfo_path)
            disc_arch = disc_info.arch
        except Exception as ex:  # pylint: disable=broad-except
            log.warning(".discinfo file can't be loaded: %s", ex)
            continue

        log.debug("discArch = %s", disc_arch)
        if disc_arch != arch:
            log.warning("Architectures mismatch in find_first_iso_image: %s != %s",
                        disc_arch, arch)
            blivet.util.umount(mount_path)
            continue