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 _main_worker(self):
      workers_running = self.count_workers_alive()
  
      while workers_running > 0 and not self.join_signal.is_set():
          # wait for a new batch in the source queue and load it
          try:
              batch_str = self._queue_internal.get(timeout=0.1)
              if batch_str == "":
                  workers_running -= 1
              else:
                  self.queue.put(batch_str)
          except QueueEmpty:
              time.sleep(0.01)
          except (EOFError, BrokenPipeError):
              break
  
          workers_running = self.count_workers_alive()
  
      # All workers have finished, move the remaining entries from internal
      # to external queue
      while True:
          try:
              batch_str = self._queue_internal.get(timeout=0.005)
              if batch_str != "":
                  self.queue.put(batch_str)
          except QueueEmpty:
              break
          except (EOFError, BrokenPipeError):
              break
  
      self.queue.put(pickle.dumps(None, protocol=-1))
      time.sleep(0.01)
  
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 4 for calling the BatchLoader obj's underlying member method code with example usage: obj._main_worker() without return types