class_docstr: `The SUN397 Data Set <https://vision.princeton.edu/projects/2010/SUN/>`_.
  
  The SUN397 or Scene UNderstanding (SUN) is a dataset for scene recognition consisting of
  397 categories with 108'754 images.
  
  Args:
      root (string): Root directory of the dataset.
      transform (callable, optional): A function/transform that takes in a PIL image and returns a transformed
          version. E.g, ``transforms.RandomCrop``.
      target_transform (callable, optional): A function/transform that takes in the target and transforms it.
      download (bool, optional): If true, downloads the dataset from the internet and
          puts it in root directory. If dataset is already downloaded, it is not
          downloaded again.
code: def __len__(self) -> int:
      return len(self._image_files)
  
file_path: vision/torchvision/datasets/sun397.py
imports: from pathlib import Path
  from typing import Any, Callable, Optional, Tuple
  import PIL.Image
  from .utils import download_and_extract_archive
  from .vision import VisionDataset
label_desc: Use image node_id 2 for calling the SUN397 obj's underlying member method code with example usage: obj.__len__() and returns: len