code: def decrypt_data_file(
      ip,
      port,
      data_file_path,
      encrypted_primary_key_path,
      encrypted_data_key_path,
      save_path=None,
  ):
      data_key = retrieve_data_key_plaintext(
          ip, port, encrypted_primary_key_path, encrypted_data_key_path
      )
      fernet = Fernet(data_key)
      decrypted = fernet.decrypt(read_data_file(data_file_path))
      if save_path is None:
          save_path = data_file_path + ".decrypted"
      write_data_file(save_path, decrypted)
      print(
          "[INFO] Decrypt Successfully! Decrypted Output Is "
          + save_path
      )
  
file_path: BigDL/python/ppml/src/bigdl/ppml/kms/ehsm/file_operator.py
imports: from key_manager import retrieve_data_key_plaintext
  from cryptography.fernet import Fernet
  import os, csv, io
label_desc: Use image node_id 4 for calling a global function with example usage: decrypt_data_file(ip, port, data_file_path, encrypted_primary_key_path, encrypted_data_key_path, save_path) without return types