code: def define_graph(self):
      return self.python_op()
  
imports: import numpy
  import nvidia.dali.ops
  import nvidia.dali.plugin.tf
  import nvidia.dali.types
  import os.path
  import tensorflow
  from nvidia.dali.pipeline import Pipeline
  from nose_utils import raises
  from test_utils import get_dali_extra_path
label_desc: Use image node_id 2 for calling the PythonOperatorPipeline obj's underlying member method code with example usage: obj.define_graph() and returns: self