src/transformers/convert_slow_tokenizer.py/SpmConverter/normalizer
class SpmConverter:    def normalizer(self, proto):
        precompiled_charsmap = proto.normalizer_spec.precompiled_charsmap
        if not precompiled_charsmap:
            return normalizers.Sequence([normalizers.Replace(Regex(" {2,}"), " ")])
        else:
            return normalizers.Sequence(
                [normalizers.Precompiled(precompiled_charsmap), normalizers.Replace(Regex(" {2,}"), " ")]
            )