class_docstr: wraps an OnDisk object for use from C++ 
code: def __init__(self, oil):
      self.oil = oil
  
imports: import numpy
  import unittest
  import faiss
  import tempfile
  import os
  import io
  import sys
  import pickle
  from multiprocessing.pool import ThreadPool
label_desc: Use image node_id 1 to create a new PyOndiskInvertedLists object  with example: obj = PyOndiskInvertedLists(oil)