private void init() {
    if (!isEmpty()) {
      LOGGER.warn(
          "SubscriptionEventTsFileResponse {} is not empty when initializing (broken invariant)",
          this);
      return;
    }

    offer(
        new CachedSubscriptionPollResponse(
            SubscriptionPollResponseType.FILE_INIT.getType(),
            new FileInitPayload(tsFile.getName()),
            commitContext));
  }
The {@code SubscriptionEventTsFileResponse} class extends {@link
SubscriptionEventExtendableResponse} to manage subscription responses related to time series
files. The actual payload can include {@link FileInitPayload}, {@link FilePiecePayload}, and
{@link FileSealPayload}, allowing for detailed control over file data streaming.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/subscription/event/response/SubscriptionEventTsFileResponse.java