code: def __del__(self):
      logging.info(f"Flipped {self.flip_cnt}")
  
imports: from typing import Optional
  from parlai.core.message import Message
  from parlai.core.mutators import MessageMutator, register_mutator
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
  from parlai.utils.data import DatatypeHelper
  import hashlib
  import parlai.utils.logging
  import copy
label_desc: Use image node_id 4 for calling the FlipClassificationLabelMutator obj's underlying member method code with example usage: obj.__del__() without return types