code: def __iter__(self):
      yield from self._benchmark.stream_definitions.keys()
  
imports: from typing import Iterable, Mapping, Optional, Sequence, Set, Tuple, TypeVar, List, Callable, Union, overload
  import warnings
  from avalanche.benchmarks.scenarios.deprecated.dataset_scenario import ClassesTimelineCLScenario, DatasetScenario, FactoryBasedStream, TStreamsUserDict
  from avalanche.benchmarks.scenarios.deprecated import AbstractClassTimelineExperience
  from avalanche.benchmarks.utils.data import AvalancheDataset
  from avalanche.benchmarks.utils.dataset_utils import manage_advanced_indexing
  from avalanche.benchmarks.utils.detection_dataset import DetectionDataset
label_desc: Use image node_id 4 for calling the _LazyStreamClassesInDetectionExps obj's underlying member method code with example usage: obj.__iter__() without return types