the digest under which an image store holds this document's image. A document given
whole (a string, bytes) is hashed by the loader; a stream is read once, so its digest is
only known after it has been parsed, and the store is consulted for it only when the
caller names the key here (the loader logs the digest it computed, for a later run).
the digest under which an image store holds this document's image. A document given whole (a string, bytes) is hashed by the loader; a stream is read once, so its digest is only known after it has been parsed, and the store is consulted for it only when the caller names the key here (the loader logs the digest it computed, for a later run).