code: def shot_noise_ref(x, factor):
      x = np.array(x, dtype=np.float32)
      return (
          np.clip(np.random.poisson(x / factor) * factor, 0, 255)
      ).astype(np.uint8)
  
file_path: DALI/dali/test/python/operator_1/test_noise_shot.py
imports: from nvidia.dali import pipeline_def
  import nvidia.dali.fn
  import nvidia.dali.types
  import random
  import numpy
  import os
  from test_utils import get_dali_extra_path
  from test_noise_utils import PSNR
label_desc: Use image node_id 1 for calling a global function with example usage: shot_noise_ref(x, factor) and returns: np