Analyze uses regular ZODB storage API: .iterator() & friends. This way
it should be possible apply it not only to FileStorage, but to other
type of storages as well - for example to NEO and ZEO.

Use zodbtools.util.storageFromURL to open a storage by knowing its URL.
Preserve support to directly apply zodbanalyze to FileStorage deltas.

/reviewed-on nexedi/zodbtools!7