code: def file_checksum(fname):
      hash_func = hashlib.sha256()
      with open(fname, "rb") as f:
          for chunk in iter(lambda: f.read(4096), b""):
              hash_func.update(chunk)
      return hash_func.hexdigest()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import inspect
  import hashlib
  import filelock
  import errno
  import os
  import sys
  import shutil
  import traceback
label_desc: Use image node_id 4 for calling a global function with example usage: file_checksum(fname) and returns: hash_func