class_docstr: Produce images read from a list of zip files. 
code: def size(self):
      return len(self.archivefiles)
  
imports: import argparse
  import numpy
  import os
  import zipfile
  import cv2
  from tensorpack import LMDBSerializer, MapDataComponent, RNGDataFlow
label_desc: Use image node_id 4 for calling the ImageDataFromZIPFile obj's underlying member method code with example usage: obj.size() and returns: len