code: def reference_pipeline(
      flip_vertical, flip_horizontal, ref_batch_size=max_batch_size
  ):
      pipeline = Pipeline(ref_batch_size, num_threads, device_id)
      with pipeline:
          data, _ = fn.readers.file(file_root=images_dir)
          img = fn.decoders.image(data)
          flipped = fn.flip(
              img, horizontal=flip_horizontal, vertical=flip_vertical
          )
          pipeline.set_outputs(flipped, img)
      return pipeline
  
file_path: DALI/dali/test/python/test_pipeline_decorator.py
imports: from nvidia.dali import Pipeline, pipeline_def
  from nose.tools import nottest
  from nose_utils import raises
  import nvidia.dali.fn
  from test_utils import get_dali_extra_path, compare_pipelines
  import os
label_desc: Use image node_id 1 for calling a global function with example usage: reference_pipeline(flip_vertical, flip_horizontal, ref_batch_size) and returns: pipeline