code: def flip_pipe(dev):
      input = fn.external_source(name="input", device=dev)
      return fn.flip(input, horizontal=True)
  
file_path: DALI/dali/test/python/operator_2/test_split_merge.py
imports: from nvidia.dali.pipeline import pipeline_def, Pipeline
  import nvidia.dali.fn
  import nvidia.dali.types
  import numpy
  from test_utils import check_batch, RandomlyShapedDataIterator
  from nose_utils import assert_raises
  from nose2.tools import params
label_desc: Use image node_id 3 for calling a global function with example usage: flip_pipe(dev) and returns: fn