# assert not self._multi_task, "you cannot fit_reader in trainer when a train is wrapper by MultiHeadTrainer."
# load data
# load data
assertself._train_init_progisnotNoneorself._pred_init_progisnotNone,"You need to build_forward or build_predict_head first to prepare input features."
assertself._shape_and_dtypesisnotNoneorself._pred_shape_and_dtypesisnotNone,"You need to build_forward or build_predict_head first to prepare input features."