code: def checksum(dpath):
      """
      Checksum on a given file.
  
      :param dpath: path to the downloaded file.
      """
      sha256_hash = hashlib.sha256()
      with open(dpath, "rb") as f:
          for byte_block in iter(lambda: f.read(65536), b""):
              sha256_hash.update(byte_block)
          return sha256_hash.hexdigest()
  
label_desc: Use image node_id 1 for calling a global function with example usage: checksum(dpath) and returns: sha256_hash