code: def encrypt_buffer(self, buffer, encrypted_buffer):
      content = buffer.getvalue()
      encrypted_content = self.secret_key.encrypt(content)
      encrypted_buffer.write(encrypted_content)
  
imports: import torch
  from torch.utils.data import Dataset
  import io
  import os
  import pathlib
  from cryptography.fernet import Fernet
  from typing import BinaryIO, Union, IO, Optional
  import pickle
  from bigdl.nano.utils.common import invalidInputError
label_desc: Use image node_id 2 for calling the _buf_operator obj's underlying member method code with example usage: obj.encrypt_buffer(buffer, encrypted_buffer) without return types