code: @CheckForNull
      public Node getNode() {
          Jenkins j = Jenkins.getInstanceOrNull(); // TODO confirm safe to assume non-null and use getInstance()
          if (j == null) {
              return null;
          }
          if (nodeName == null) {
              return j;
          }
          return j.getNode(nodeName);
      }
docs: Returns the {@link Node} that this computer represents.
  
  @return
  null if the configuration has changed and the node is removed, yet the corresponding {@link Computer}
  is not yet gone.