code: def _postprocess_image(image):
      if image.ndim == 2:
          # image is greyscale
          image = image[..., None]
      return image.transpose(2, 0, 1)
  
imports: import bisect
  import io
  import os
  import threading
  import zipfile
  import numpy
  import six
  import chainer
  from chainer.dataset import dataset_mixin
label_desc: Use image node_id 2 for calling a global function with example usage: _postprocess_image(image) and returns: image