def message(transformer = Undefined)
      return @custom_message if @custom_message

      transformer = self.transformer if Undefined.equal?(transformer)

      transformer.transform(self)
    end
def message(transformer = Undefined)
      return @custom_message if @custom_message

      transformer = self.transformer if Undefined.equal?(transformer)

      transformer.transform(self)
    end
Configure a Violation instance

 @param [Object] resource
   the validated object
 @param [String, #call, Hash] message
   an optional custom message for this Violation
 @param [Hash] options
   options hash for configuring concrete subclasses

 @api public
 @api public