code: private String doBackwardPathOnly(final FedoraResource resource) {
  
          final String path = reverse.convert(resource.getPath());
          if (path == null) {
              throw new RepositoryRuntimeException("Unable to process reverse chain for resource " + resource);
          }
  
          return convertToExternalPath(path);
      }
docs: Get only the resource path to this resource, before embedding it in a full URI
  @param resource with desired path
  @return path