code: def decrypt_buf(
      ip,
      port,
      buf: io.BytesIO,
      decrypted_buf: io.BytesIO,
      encrypted_primary_key_path,
      encrypted_data_key_path,
  ):
      data_key = retrieve_data_key_plaintext(
          ip, port, encrypted_primary_key_path, encrypted_data_key_path
      )
      fernet = Fernet(data_key)
      decrypted_content = fernet.decrypt(buf.getvalue())
      decrypted_buf.write(decrypted_content)
  
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 5 for calling a global function with example usage: decrypt_buf(ip, port, buf, decrypted_buf, encrypted_primary_key_path, encrypted_data_key_path) without return types