code: def _update_tracker(self, event, instance):
      if event == Events.OPTIMIZATION_STEP:
          self._iterations += 1
  
          if instance.max is None:
              return
  
          current_max = instance.max
  
          if (
              self._previous_max is None
              or current_max["target"] > self._previous_max
          ):
              self._previous_max = current_max["target"]
              self._previous_max_params = current_max["params"]
  
file_path: BayesianOptimization/bayes_opt/observer.py
imports: from datetime import datetime
  from .event import Events
label_desc: Use image node_id 2 for calling the _Tracker obj's underlying member method code with example usage: obj._update_tracker(event, instance) without return types