code: def __call__(self, arg):
      if self.batch_info:
          assert isinstance(
              arg, types.BatchInfo
          ), f"Expected BatchInfo instance as cb argument, got {arg}"
          iteration = arg.iteration
          epoch_idx = arg.epoch_idx
      else:
          assert isinstance(
              arg, int
          ), "Expected integer as cb argument, got {}".format(arg)
          iteration = arg
          epoch_idx = -1
      if iteration >= self.epoch_size:
          raise StopIteration
      return [
          np.array([iteration, epoch_idx], dtype=np.int32)
          for _ in range(self.batch_size)
      ]
  
imports: import random
  import nvidia.dali.fn
  import nvidia.dali.ops
  import nvidia.dali.types
  import numpy
  from nvidia.dali import Pipeline, pipeline_def
  from test_utils import check_batch
  from nose_utils import raises, assert_warns, assert_raises
  from nvidia.dali.types import DALIDataType
  from numpy.random import default_rng
label_desc: Use image node_id 2 for calling the BatchCb obj's underlying member method code with example usage: obj.__call__(arg) and returns: unknown