code: def __next__(self):
      self.count += 1
      return [
          np.array([self.pid, self.count]) for i in range(self.count)
      ]
  
imports: from nvidia.dali._multiproc.pool import WorkerPool
  from nvidia.dali._multiproc.messages import TaskArgs, SampleRange
  from contextlib import closing
  from nvidia.dali._utils.external_source_impl import get_callback_from_source
  from nvidia.dali.types import SampleInfo
  from functools import wraps
  import numpy
  import os
  from nose.tools import with_setup
  from nose_utils import raises
  from test_pool_utils import capture_processes, setup_function, teardown_function
label_desc: Use image node_id 3 for calling the IteratorCb obj's underlying member method code with example usage: obj.__next__() and returns: unknown