Set a cached item by key

        WARN: Regardless if the item is already in the cache,
              it will be udpated with the new value.

def set(self, key, val, bucket):
        """ Set a cached item by key

        WARN: Regardless if the item is already in the cache,
              it will be udpated with the new value.
        """

        if bucket not in self._cache:
            self._cache[bucket] = {}

        self._cache[bucket][key] = val