public Optional<CachedLayer> retrieve(DescriptorDigest layerDigest)
      throws IOException, CacheCorruptedException {
    return cacheStorageReader.retrieve(layerDigest);
  }
Retrieves the {@link CachedLayer} for the layer with digest {@code layerDigest}.

@param layerDigest the layer digest
@return the {@link CachedLayer} referenced by the layer digest, if found
@throws CacheCorruptedException if the cache was found to be corrupted
@throws IOException if an I/O exception occurs
jib-core/src/main/java/com/google/cloud/tools/jib/cache/Cache.java