public Collection<Long> objectIds() {
        if (objects == null || registryRef == RegistryRef.NOOP) {
            return Collections.emptyList();
        }

        return registryRef.inLock(() -> objects.keySet(registryRef.epoch()));
    }
Represents the S3 objects in the metadata image.
<p>
This class is thread-safe.
metadata/src/main/java/org/apache/kafka/image/S3ObjectsImage.java