class_docstr: The Penn-Fudan Pedestrian detection and segmentation dataset
  
  Adapted from the "TorchVision Object Detection Finetuning Tutorial":
  https://pytorch.org/tutorials/intermediate/torchvision_tutorial.html
code: def __len__(self):
      return len(self.imgs)
  
file_path: avalanche/avalanche/benchmarks/datasets/penn_fudan/penn_fudan_dataset.py
imports: from pathlib import Path
  from typing import Dict, List, Optional, Sequence, Union
  import numpy
  import torch
  from PIL import Image
  from torchvision.datasets.folder import default_loader
  from avalanche.benchmarks.datasets import SimpleDownloadableDataset, default_dataset_location
  from avalanche.benchmarks.datasets.penn_fudan.penn_fudan_data import penn_fudan_data
label_desc: Use image node_id 5 for calling the PennFudanDataset obj's underlying member method code with example usage: obj.__len__() and returns: len