class_docstr: USPS Dataset.
  
  Args:
      root (string): Root directory of dataset where dataset file exist.
      train (bool, optional): If True, resample from dataset randomly.
      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.
      transform (callable, optional): A function/transform that takes in
          an PIL image and returns a transformed version.
          E.g, ``transforms.RandomCrop``
docstr: Return size of dataset.
docstr_tok: ["Return","size","of","dataset","."]
code: def __len__(self):
      """Return size of dataset."""
      return self.dataset_size
  
file_path: pykale/kale/loaddata/usps.py
imports: import gzip
  import logging
  import os
  import pickle
  import urllib
  import numpy
  import torch
  import torch.utils.data
label_desc: Use image node_id 3 for calling the USPS obj's underlying member method code with example usage: obj.__len__() and returns: self