Function OldSerialization

src/common/error_msg.h:65–74

}

constexpr StringView OldSerialization() {
  return R"doc(If you are loading a serialized model (like pickle in Python, RDS in R) or
configuration generated by an older version of XGBoost, please export the model by calling
`Booster.save_model` from that version first, then load it back in current version. See:

    https://xgboost.readthedocs.io/en/stable/tutorials/saving_model.html

for more details about differences between saving model and serializing.
)doc";
}

inline void WarnOldSerialization() {
  // Display it once is enough. Otherwise this can be really verbose in distributed