code: @SuppressWarnings("unused")
      public Object readResolve() {
          if (configVersion < 1) {
              if (isNull(nodeProperties)) nodeProperties = new ArrayList<>();
              nodeProperties.add(new DockerNodeProperty("DOCKER_CONTAINER_ID", "JENKINS_CLOUD_ID", "DOCKER_HOST"));
              configVersion = 1;
          }
  
          // real @Nonnull
          if (mode == null) {
              mode = Node.Mode.NORMAL;
          }
  
          if (retentionStrategy == null) {
              retentionStrategy = new DockerOnceRetentionStrategy(10);
          }
  
          try {
              labelSet = Label.parse(getLabelString()); // fails sometimes under debugger
          } catch (Throwable t) {
              LOG.error("Can't parse labels: {}", t);
          }
  
          return this;
      }
docs: Initializes data structure that we don't persist.