public BrokerRegistration broker(int nodeId) {
        Optional<BrokerRegistration> result = changedBrokers.get(nodeId);
        if (result != null) {
            return result.orElse(null);
        }
        return image.broker(nodeId);
    }
Represents changes to the cluster in the metadata image.
metadata/src/main/java/org/apache/kafka/image/ClusterDelta.java