code: def pipe():
      jpegs = dali.fn.external_source(dtype=types.UINT8, name="source")
      decoded = dali.fn.decoders.image(
          jpegs, device="mixed", output_type=types.GRAY
      )
      normalized = dali.fn.crop_mirror_normalize(
          decoded,
          mean=[0.1307 * 255],
          std=[0.3081 * 255],
      )
      return normalized
  
imports: import nvidia.dali
  import nvidia.dali.types
  import yaml
label_desc: Use image node_id 2 for calling a global function with example usage: pipe() and returns: normalized