code: def mock_post_render_func(img, **kwargs):
      from PIL import ImageDraw
  
      (x, y) = (5, 5)
      info = "x={} / y={} / z={}, w={}, h={}".format(
          kwargs["x"], kwargs["y"], kwargs["z"], img.width, img.height
      )
  
      draw = ImageDraw.Draw(img)
      draw.text((x, y), info, fill="rgb(255, 255, 255)")
      return img
  
file_path: datashader/datashader/tests/test_tiles.py
imports: from __future__ import annotations
  import datashader
  import datashader.transfer_functions
  from datashader.colors import viridis
  from datashader.tiles import render_tiles
  from datashader.tiles import gen_super_tiles
  from datashader.tiles import _get_super_tile_min_max
  from datashader.tiles import calculate_zoom_level_stats
  from datashader.tiles import MercatorTileDefinition
  import numpy
  import pandas
label_desc: Use image node_id 4 for calling a global function with example usage: mock_post_render_func(img) and returns: img