code: def __init__(self):
      super().__init__()
      # 0=RandomPolicy, 1=1st main policy snapshot,
      # 2=2nd main policy snapshot, etc..
      self.current_opponent = 0
  
imports: import argparse
  import os
  import sys
  import numpy
  import ray
  from ray import air, tune
  from ray.rllib.algorithms.callbacks import DefaultCallbacks
  from ray.rllib.env.utils import try_import_pyspiel, try_import_open_spiel
  from ray.rllib.env.wrappers.open_spiel import OpenSpielEnv
  from ray.rllib.examples.policy.random_policy import RandomPolicy
  from ray.rllib.policy.policy import PolicySpec
  from ray.rllib.utils.test_utils import check_learning_achieved
  from ray.tune import CLIReporter, register_env
  from ray.tune.registry import get_trainable_cls
  from ray.rllib.core.rl_module.rl_module import SingleAgentRLModuleSpec
  from ray.rllib.core.rl_module.marl_module import MultiAgentRLModuleSpec
  from ray.rllib.examples.rl_module.random_rl_module import RandomRLModule
  from open_spiel.python.rl_environment import Environment
label_desc: Use image node_id 1 to create a new SelfPlayCallback object from inherited base classes: DefaultCallbacks with example: obj = SelfPlayCallback()