class_docstr: Call multiple callbacks at once.
class_docstr_tok: ["Call","multiple","callbacks","at","once","."]
code: def __getitem__(self, i: int) -> "Callback":
      return self._callbacks[i]
  
imports: from abc import ABCMeta
  import glob
  import os
  from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
  import warnings
  from ray.util.annotations import PublicAPI, DeveloperAPI
  from ray.tune.utils.util import _atomic_save, _load_newest_checkpoint
label_desc: Use image node_id 20 for calling the CallbackList obj's underlying member method code with example usage: obj.__getitem__(i) and returns: self