output method
Implementation
@override
void output(OutputEvent event) {
  if (buffer.length == bufferSize) {
    buffer.removeFirst();
  }
  buffer.add(event);
  secondOutput?.output(event);
}@override
void output(OutputEvent event) {
  if (buffer.length == bufferSize) {
    buffer.removeFirst();
  }
  buffer.add(event);
  secondOutput?.output(event);
}