code: function isCached(config) {
          var cache;
          var defaultCache = $cacheFactory.get('$http');
          var defaults = $httpProvider.defaults;
  
          // Choose the proper cache source. Borrowed from angular: $http service
          if ((config.cache || defaults.cache) && config.cache !== false &&
            (config.method === 'GET' || config.method === 'JSONP')) {
              cache = angular.isObject(config.cache) ? config.cache
                : angular.isObject(defaults.cache) ? defaults.cache
                : defaultCache;
          }
  
          var cached = cache !== undefined ?
            cache.get(config.url) !== undefined : false;
  
          if (config.cached !== undefined && cached !== config.cached) {
            return config.cached;
          }
          config.cached = cached;
          return cached;
        }
docs: Determine if the response has already been cached
  @param  {Object}  config the config option from the request
  @return {Boolean} retrns true if cached, otherwise false