code: private File getNodesDir() throws IOException {
          final File nodesDir = new File(jenkins.getRootDir(), "nodes");
          if (!nodesDir.isDirectory() && !nodesDir.mkdirs()) {
              throw new IOException(String.format("Could not mkdirs %s", nodesDir));
          }
          return nodesDir;
      }
docs: Returns the directory that the nodes are stored in.
  
  @return the directory that the nodes are stored in.
  @throws IOException