class_docstr: Stream-51 Pytorch Dataset
code: def _download_error_message(self) -> str:
      return (
          "[Stream-51] Error downloading the dataset. Consider "
          "downloading it manually at: "
          + stream51_data.name[1]
          + " and placing it in: "
          + str(self.root)
      )
  
imports: import os
  import shutil
  import json
  import random
  from pathlib import Path
  from typing import Any, List, Optional, Sequence, Tuple, TypeVar, Union
  from torchvision.datasets.folder import default_loader
  from zipfile import ZipFile
  from torchvision.transforms import ToTensor
  from avalanche.benchmarks.datasets import DownloadableDataset, default_dataset_location
  from avalanche.benchmarks.datasets.stream51 import stream51_data
label_desc: Use image node_id 4 for calling the Stream51 obj's underlying member method code with example usage: obj._download_error_message() and returns: unknown