code: def on_start(self, smbo: smac.main.smbo.SMBO) -> None:
      print("Let's start!")
      print("")
  
file_path: SMAC3/examples/1_basics/4_callback.py
imports: from __future__ import annotations
  from ConfigSpace import Configuration, ConfigurationSpace, Float
  import smac
  from smac import Callback
  from smac import HyperparameterOptimizationFacade
  from smac import Scenario
  from smac.runhistory import TrialInfo, TrialValue
label_desc: Use image node_id 2 for calling the CustomCallback obj's underlying member method code with example usage: obj.on_start(smbo) without return types