src/transformers/convert_slow_tokenizer.py/NllbConverter/post_processor
class NllbConverter:    def post_processor(self):
        return processors.TemplateProcessing(
            single="eng_Latn $A </s>",
            pair="eng_Latn $A $B </s>",
            special_tokens=[
                ("eng_Latn", self.original_tokenizer.convert_tokens_to_ids("eng_Latn")),
                ("</s>", self.original_tokenizer.convert_tokens_to_ids("</s>")),
            ],
        )