code: def read_mk(fobj, start_length, size):
      # Alpha masks seem to be uncompressed
      start = start_length[0]
      fobj.seek(start)
      pixel_size = (size[0] * size[2], size[1] * size[2])
      sizesq = pixel_size[0] * pixel_size[1]
      band = Image.frombuffer(
          "L", pixel_size, fobj.read(sizesq), "raw", "L", 0, 1
      )
      return {"A": band}
  
imports: import io
  import os
  import struct
  import sys
  from PIL import Image, ImageFile, PngImagePlugin, features
label_desc: Use image node_id 4 for calling a global function with example usage: read_mk(fobj, start_length, size) and returns: dict