code: public static void addPathAlterationObserver(PathAlterationObserverScheduler monitor, PathAlterationListener listener,
        Path rootDirPath)
        throws IOException {
      PathAlterationObserver observer = new PathAlterationObserver(rootDirPath);
      observer.addListener(listener);
      monitor.addObserver(observer);
    }
docs: Add {@link PathAlterationObserverScheduler}s for the given
  root directory and any nested subdirectories under the root directory to the given
  {@link PathAlterationObserverScheduler}.
  
  @param monitor a {@link PathAlterationObserverScheduler}
  @param listener a {@link org.apache.gobblin.util.filesystem.PathAlterationListener}
  @param rootDirPath root directory