code: def flush(self, epoch: int):
      logger.info(f"Epoch {epoch} ended")
  
      for observer in self._aggregating_observers.values():
          observer.flush()
  
file_path: ReAgent/reagent/reporting/reporter_base.py
imports: import abc
  import logging
  from typing import Dict
  import torch
  from reagent.core.observers import CompositeObserver, EpochEndObserver, IntervalAggregatingObserver, ValueListObserver
  from reagent.core.result_registries import TrainingReport
  from reagent.core.tracker import ObservableMixin
  from reagent.core.utils import lazy_property
label_desc: Use image node_id 3 for calling the ReporterBase obj's underlying member method code with example usage: obj.flush(epoch) without return types