code: def message_mutation(self, message: Message) -> Message:
      if not self.is_training:
          return message
      else:
          return super().message_mutation(message)
  
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 2 for calling the FlipClassificationLabelTrainOnlyMutator obj's underlying member method code with example usage: obj.message_mutation(message) and returns: message, super