public void finishSnapshot() {
        for (Entry<ScramMechanism, Map<String, ScramCredentialData>> mechanismEntry : image.mechanisms().entrySet()) {
            Map<String, Optional<ScramCredentialData>> userNameMap =
                changes.computeIfAbsent(mechanismEntry.getKey(), __ -> new HashMap<>());
            for (String userName : mechanismEntry.getValue().keySet()) {
                if (!userNameMap.containsKey(userName)) {
                    userNameMap.put(userName, Optional.empty());
                }
            }
        }
    }
Represents changes to a topic in the metadata image.
metadata/src/main/java/org/apache/kafka/image/ScramDelta.java