class_docstr: A wrapper around a result or an error.
  
  This is used to return data from FaultTolerantActorManager
  that allows us to distinguish between error and actual results.
class_docstr_tok: ["A","wrapper","around","a","result","or","an","error",".","This","is","used","to","return","data","from","FaultTolerantActorManager","that","allows","us","to","distinguish","between","error","and","actual","results","."]
code: def ok(self):
      return self._error is None
  
imports: from collections import defaultdict
  import copy
  from dataclasses import dataclass
  import logging
  import sys
  import time
  from typing import Any, Callable, Dict, Iterator, List, Mapping, Optional, Tuple, Union
  import ray
  from ray.actor import ActorHandle
  from ray.exceptions import RayActorError, RayError, RayTaskError
  from ray.rllib.utils.typing import T
  from ray.util.annotations import DeveloperAPI
label_desc: Use image node_id 2 for calling the ResultOrError obj's underlying member method code with example usage: obj.ok() and returns: unknown