code: def nextheader(fobj):
      return struct.unpack(">4sI", fobj.read(HEADERSIZE))
  
imports: import io
  import os
  import shutil
  import struct
  import sys
  import tempfile
  from PIL import Image, ImageFile, PngImagePlugin
  from PIL._binary import i8
label_desc: Use image node_id 1 for calling a global function with example usage: nextheader(fobj) and returns: struct