docstr: Returns metric history.
code: def after_training(self, **kw):
      """Returns metric history."""
      self.trainer.return_values.update(self.metric_history)
  
file_path: flair/flair/trainers/plugins/loggers/metric_history.py
imports: import logging
  from typing import Any, Dict, Mapping
  from flair.trainers.plugins.base import TrainerPlugin
label_desc: Use image node_id 3 for calling the MetricHistoryPlugin obj's underlying member method code with example usage: obj.after_training() without return types