Function expected_boot_image_ids 

pub(crate) fn expected_boot_image_ids(
    v1: Option<Sha512HashValue>,
    v2: Option<Sha512HashValue>,
    selected: &Sha512HashValue,
    selected_format: FormatVersion,
) -> ExpectedBootImageIds

Associate every accepted boot image with its EROFS serialization format. A UKI’s V1 candidate must never be accepted merely because its digest is a valid V2 image (or vice versa). selected is the freshly generated image; recovered images are added with their actual format by the recovery path.