src/transformers/convert_slow_tokenizer.py/T5Converter/post_processor
class T5Converter:    def post_processor(self):
        return processors.TemplateProcessing(
            single=["$A", "</s>"],
            pair=["$A", "</s>", "$B", "</s>"],
            special_tokens=[
                ("</s>", self.original_tokenizer.convert_tokens_to_ids("</s>")),
            ],
        )