code: def layout_str(dim, channel_first):
      s = "DHW" if dim == 3 else "HW"
      s = "C" + s if channel_first else s + "C"
      return s
  
imports: import cv2
  import functools
  import math
  import numpy
  import nvidia.dali
  import nvidia.dali.fn
  import nvidia.dali.types
  import os.path
  from nvidia.dali import Pipeline, pipeline_def
  from nvidia.dali.data_node import DataNode
  from test_utils import check_batch, get_dali_extra_path, as_array
  import PIL.Image
label_desc: Use image node_id 1 for calling a global function with example usage: layout_str(dim, channel_first) and returns: s