src/transformers/convert_slow_tokenizer.py/XLMRobertaConverter/vocab
class XLMRobertaConverter:    def vocab(self, proto):
        vocab = [
            ("<s>", 0.0),
            ("<pad>", 0.0),
            ("</s>", 0.0),
            ("<unk>", 0.0),
        ]
        vocab += [(piece.piece, piece.score) for piece in proto.pieces[3:]]
        vocab += [("<mask>", 0.0)]
        return vocab