Back Translation in Text Augmentation by nlpaug

English is one of the languages which has lots of training data for translation while some language may not has enough data to train a machine translation model. Sennrich et al. used the back-translation method to generate more training data to improve translation model performance. Given that we want to train a model for translating English (source language) Cantonese (target language) and there is not enough training data for Cantonese. Back-translation is translating target language to source language and mixing both original source sentences and back-translated sentences to train a model. So the number of training data from the source language to target language can be increased.