code: def check_sum():
      """
      Return a long which can be used to know if any .py files have changed.
      """
      val = 0
      for root, dirs, files in os.walk(os.getcwd()):
          for extension in EXTENSIONS:
              for f in fnmatch.filter(files, extension):
                  stats = os.stat(os.path.join(root, f))
                  val += stats[stat.ST_SIZE] + stats[stat.ST_MTIME]
      return val
  
imports: import os
  import stat
  import time
  import datetime
  import sys
  import fnmatch
label_desc: Use image node_id 1 for calling a global function with example usage: check_sum() and returns: val