code: def DeregisterDecrypter(cls, decrypter):
      
      encryption_method = decrypter.ENCRYPTION_METHOD.lower()
      if encryption_method not in cls._decrypters:
        raise KeyError(
            'Decrypter for encryption method: {0:s} not set.'.format(
                decrypter.ENCRYPTION_METHOD))
  
      del cls._decrypters[encryption_method]
docs: Deregisters a decrypter for a specific encryption method.
  
      Args:
        decrypter (type): decrypter class.
  
      Raises:
        KeyError: if the corresponding decrypter is not set.