code: private File baseDir() throws IOException {
          if (baseDir == null) {
              baseDir = File.createTempFile("fcrepo-dto", null);
              if (!baseDir.delete()) {
                  throw new IOException("Can't delete temp file " + baseDir);
              }
              if (!baseDir.mkdir()) {
                  throw new IOException("Can't create temp dir " + baseDir);
              }
          }
          return baseDir;
      }
docs: allocates the temporary base directory lazily