before_sent:  This improves standard back-translation and also enables the use of iterative back-translation on language pairs that underperformed using standard back-translation.
before_sent_with_intent: <fluency>  This improves standard back-translation and also enables the use of iterative back-translation on language pairs that underperformed using standard back-translation.
after_sent:  This improves standard back-translation and also enabling the use of iterative back-translation on language pairs that underperformed using standard back-translation.