class_docstr: A helper metaclass to ensure container classes (e.g. CallbackList) have
  implemented all the callback methods (e.g. `on_*`).
class_docstr_tok: ["A","helper","metaclass","to","ensure","container","classes","(","e.g",".","CallbackList",")","have","implemented","all","the","callback","methods","(","e.g",".","`","on_","*","`",")","."]
code: def __new__(
      mcs, name: str, bases: Tuple[type], attrs: Dict[str, Any]
  ) -> type:
      cls = super().__new__(mcs, name, bases, attrs)
  
      if mcs.need_check(cls, name, bases, attrs):
          mcs.check(cls, name, bases, attrs)
  
      return cls
  
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 1 for calling the _CallbackMeta obj's underlying member method code with example usage: obj.__new__(mcs, name, bases, attrs) and returns: cls