code: def _dummy_gen(size=5):
      yield np.random.rand(size, 28, 28, 1), np.random.randint(
          low=0, high=10, size=(size, 10)
      )
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import unittest
  import tensorflow
  import numpy
  from keras.preprocessing.image import ImageDataGenerator
  from art.data_generators import KerasDataGenerator, PyTorchDataGenerator, MXDataGenerator, TensorFlowDataGenerator
  from art.data_generators import TensorFlowV2DataGenerator, NumpyDataGenerator
  from tests.utils import master_seed
label_desc: Use image node_id 9 for calling the TestKerasDataGenerator obj's underlying member method code with example usage: obj._dummy_gen(size) without return types