class_docstr: **Deprecated**. Load batches in the background.
  
  Deprecated. Use ``imgaug.multicore.Pool`` instead.
  
  Loaded batches can be accesses using :attr:`imgaug.BatchLoader.queue`.
  
  Parameters
  ----------
  load_batch_func : callable or generator
      Generator or generator function (i.e. function that yields Batch
      objects) or a function that returns a list of Batch objects.
      Background loading automatically stops when the last batch was yielded
      or the last batch in the list was reached.
  
  queue_size : int, optional
      Maximum number of batches to store in the queue. May be set higher
      for small images and/or small batches.
  
  nb_workers : int, optional
      Number of workers to run in the background.
  
  threaded : bool, optional
      Whether to run the background processes using threads (True) or full
      processes (False).
code: def count_workers_alive(self):
      return sum([int(worker.is_alive()) for worker in self.workers])
  
imports: from __future__ import print_function, division, absolute_import
  import sys
  import multiprocessing
  import threading
  import traceback
  import time
  import random
  import platform
  import numpy
  import cv2
  import imgaug.imgaug
  import imgaug.random
  from imgaug.augmentables.batches import Batch, UnnormalizedBatch
label_desc: Use image node_id 2 for calling the BatchLoader obj's underlying member method code with example usage: obj.count_workers_alive() and returns: sum