presto-orc/src/main/java/io/prestosql/orc/stream/PresentOutputStream.java/PresentOutputStream/getCheckpoints
class PresentOutputStream:    public Optional<List<BooleanStreamCheckpoint>> getCheckpoints()
    {
        checkArgument(closed);
        if (booleanOutputStream == null) {
            return Optional.empty();
        }
        return Optional.of(booleanOutputStream.getCheckpoints());
    }