@CanIgnoreReturnValue
    public Builder setWatchServiceConfiguration(WatchServiceConfiguration config) {
      this.watchServiceConfig = checkNotNull(config);
      return this;
    }
Sets the configuration that {@link WatchService} instances created by the file system should
use. The default configuration polls watched directories for changes every 5 seconds.

@since 1.1
jimfs/src/main/java/com/google/common/jimfs/Configuration.java