code: def define_graph(self):
      output = self.input(name="Reader")
      return output
  
imports: import os
  import math
  from test_utils import get_gpu_num
  from test_utils import get_dali_extra_path
  import nvidia.dali.ops
  import nvidia.dali.types
  from nvidia.dali.pipeline import Pipeline, pipeline_def
  import nvidia.dali.fn
  import numpy
  import tempfile
  from test_utils import check_output_pattern
  from nose_utils import assert_raises, raises
label_desc: Use image node_id 2 for calling the VideoPipeRoot obj's underlying member method code with example usage: obj.define_graph() and returns: output