code: public static DocPath forRoot(PackageElement pkgElement) {
          String name = (pkgElement == null || pkgElement.isUnnamed())
                  ? ""
                  : pkgElement.getQualifiedName().toString();
          return new DocPath(name.replace('.', '/').replaceAll("[^/]+", ".."));
      }
docs: Return the inverse path for a package.
  For example, if the package is java.lang,
  the inverse path is ../...