code: def roll(self):
          
          rem = []
          for key, item in self._cache.items():
              if item[0] > self.max_age:
                  rem.append(key)
              item[0] += 1
  
          for key in rem:
              logger.debug("TransformCache remove: %s", key)
              del self._cache[key]
docs: Increase the age of all items in the cache by 1. Items whose age
          is greater than self.max_age will be removed from the cache.