code: @Reference(policy = DYNAMIC, cardinality = MULTIPLE)
      public void addRoot(final WatchedDirectory pWatchedDirectory) {
          requireNonNull(pWatchedDirectory, WATCHED_DIRECTORY_IS_NULL);
          rootInitSwitch.add(pWatchedDirectory);
      }
docs: Whiteboard bind-method for {@link WatchedDirectory} services exported by any client bundle. This
  method is called when a client exports a service which implements the {@link WatchedDirectory} interface.
  
  @param pWatchedDirectory Watched-directory service to be registered.