What does this code extend?

Given a file in a plug-in cartridge with the following code:

‘use strict’:

Var base = module.superModule;

Function applyCustomCache (req,res,next){

res.CachePeriod = 6; //eslint-disable-line no-param-reassign

res.cachePeriodUnit = ‘hours’) //eslint-disable-line no-param-reassign

next();

}

Module.exports = base;

Module.exports.applyCustomCache = applyCustomCache;

What does this code extend?
A . A controller
B. A middleware script
C. A decorator
D. A model