checkpoints.py

import pickle

ckpt = '/content/drive/MyDrive/mydumps/ck1.pickle'

def load():
  with open(ckpt, 'rb') as fp:
    chk = pickle.load(fp)
  return chk

def exists(key):
  chk = load()
  return key in chk

def save(key):
  try:
    chk = load()
  except:
    chk = set()
  chk.add(key)
  with open(ckpt, 'wb') as fp:
    pickle.dump(chk, fp)