src/transformers/pipelines/text2text_generation.py/TranslationPipeline/preprocess
class TranslationPipeline:    def preprocess(self, *args, truncation=TruncationStrategy.DO_NOT_TRUNCATE, src_lang=None, tgt_lang=None):
        if getattr(self.tokenizer, "_build_translation_inputs", None):
            return self.tokenizer._build_translation_inputs(
                *args, return_tensors=self.framework, truncation=truncation, src_lang=src_lang, tgt_lang=tgt_lang
            )
        else:
            return super()._parse_and_tokenize(*args, truncation=truncation)