class_docstr: Replace message text with empty strings.
code: def message_mutation(self, message: Message) -> Message:
      message.force_set("text", "")
      message.force_set("labels", [""])
      return message
  
imports: import os
  import unittest
  from parlai.core.message import Message
  from parlai.core.mutators import MessageMutator, register_mutator
  import parlai.utils.testing
label_desc: Use image node_id 1 for calling the DegenerateMutator obj's underlying member method code with example usage: obj.message_mutation(message) and returns: message