code: def get_sampling(im):
      # There's no subsampling when images have only 1 layer
      # (grayscale images) or when they are CMYK (4 layers),
      # so set subsampling to the default value.
      #
      # NOTE: currently Pillow can't encode JPEG to YCCK format.
      # If YCCK support is added in the future, subsampling code will have
      # to be updated (here and in JpegEncode.c) to deal with 4 layers.
      if not hasattr(im, "layers") or im.layers in (1, 4):
          return -1
      sampling = im.layer[0][1:3] + im.layer[1][1:3] + im.layer[2][1:3]
      return samplings.get(sampling, -1)
  
imports: from __future__ import annotations
  import array
  import io
  import math
  import os
  import struct
  import subprocess
  import sys
  import tempfile
  import warnings
  from .None import Image, ImageFile
  from ._binary import i16be
  from ._binary import i32be
  from ._binary import o8
  from ._binary import o16be
  from .JpegPresets import presets
label_desc: Use image node_id 9 for calling a global function with example usage: get_sampling(im) and returns: samplings, unknown