code: def max_age(self):
          
          value = defines.OptionRegistry.MAX_AGE.default
          for option in self.options:
              if option.number == defines.OptionRegistry.MAX_AGE.number:
                  value = int(option.value)
          return value
docs: Return the MaxAge of the response.
  
          :rtype : int
          :return: the MaxAge option