class_docstr: Callback to check that every method was called once at least
class_docstr_tok: ["Callback","to","check","that","every","method","was","called","once","at","least"]
code: def _on_training_end(self):
      self.calls["training_end"] = True
  
file_path: stable-baselines/tests/test_callbacks.py
imports: import os
  import shutil
  import pytest
  from stable_baselines import A2C, ACKTR, ACER, DQN, DDPG, PPO1, PPO2, SAC, TD3, TRPO
  from stable_baselines.common import make_vec_env
  from stable_baselines.common.callbacks import CallbackList, CheckpointCallback, EvalCallback, EveryNTimesteps, StopTrainingOnRewardThreshold, BaseCallback
label_desc: Use image node_id 6 for calling the CustomCallback obj's underlying member method code with example usage: obj._on_training_end() without return types