code: def __str__(self) -> str:
      return (
          f"Callback types: {self.callback_types}, "
          f"Metrics: {self.metrics}, "
          f"Evaluation frequency: {self.evaluation_freq}, "
          f"Early stopping rounds: {self.early_stopping_rounds}, "
          f"Use first metric for early stopping: {self.use_first_metric}, "
          f"Checkpoint frequency: {self.checkpoint_freq}"
      )
  
file_path: FATE/python/fate/ml/utils/callbacks.py
imports: from fate.ml.evaluation.tool import get_metric_names, get_specified_metrics
  from fate.ml.abc.module import Module
label_desc: Use image node_id 2 for calling the CallbackParam obj's underlying member method code with example usage: obj.__str__() and returns: str, self, str, self, str, self, str, self, str, self, str, self