code: function(key, value, maxAge) {
        if (!cache) return false;
        if (cache.has(key)) return false;
  
        maxAge = maxAge || this.conf.cache.maxAge;
        console.log('cache write: %s', key);
        cache.set(key, value, maxAge);
        return true;
      }
docs: /*
  Write <key, value> into cache
  if *key* already exists in cache, do not do an additional write.
  
  Return false if cache is not set or a cache write does not happen.
  Otherwise, return true if a cache-write succeeds.