code: public FileEventOptions kind(final WatchEvent.Kind<Path> kind) {
      requireNonNull(kind, "WatchEvent.Kind required.");
      kinds.add(kind);
      return this;
    }
docs: Append a kind filter.
  
  The default filter is: {@link StandardWatchEventKinds#ENTRY_CREATE},
  {@link StandardWatchEventKinds#ENTRY_DELETE} and {@link StandardWatchEventKinds#ENTRY_MODIFY}.
  
  @param kind Filter type.
  @return This options.