@Override
    final List<T> drainAll(boolean withPooledObjects) {
        assert obj != null;
        final T item = touchOrCopyAndClose(obj, withPooledObjects);
        obj = null;
        return ImmutableList.of(item);
    }
A {@link FixedStreamMessage} that only publishes one object.
core/src/main/java/com/linecorp/armeria/internal/common/stream/OneElementFixedStreamMessage.java