code: function(configStrategy) {
      let instanceKey = getInstanceKey(configStrategy);
  
      let _instance = instanceMap[instanceKey];
  
      if (!_instance) {
        _instance = new OSTCache(configStrategy);
        instanceMap[instanceKey] = _instance;
      }
  
      return _instance;
    }
docs: Fetches a cache instance if available in instanceMap. If instance is not available in
  instanceMap, it calls createCacheInstance() to create a new cache instance.
  
  @returns {cacheInstance}