public Node build() {
            return new Node(id, Optional.ofNullable(extraId), Optional.ofNullable(ipConfig).orElse(IP.Config.EMPTY), hostname, Optional.ofNullable(parentHostname),
                            flavor, Optional.ofNullable(status).orElseGet(Status::initial), state, Optional.ofNullable(allocation),
                            Optional.ofNullable(history).orElseGet(History::empty), type, Optional.ofNullable(reports).orElseGet(Reports::new),
                            Optional.ofNullable(modelName), Optional.ofNullable(reservedTo), Optional.ofNullable(exclusiveToApplicationId),
                            Optional.ofNullable(provisionedForApplicationId), Optional.ofNullable(hostTTL), Optional.ofNullable(hostEmptyAt),
                            Optional.ofNullable(exclusiveToClusterType), Optional.ofNullable(switchHostname),
                            Optional.ofNullable(trustStoreItems).orElseGet(List::of), cloudAccount, Optional.ofNullable(wireguardPubKey));
        }
The mean and mean deviation (squared difference) of a bunch of numbers
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/Node.java