code: def set(self, key, value, expires=None, future=None):
          
          # assert the values above
          with self._lock:
              try:
                  self._dict[key].set(value, expires=expires, future=future)
              except KeyError:
                  self._dict[key] = moment(value, expires=expires, future=future, lock=self._lock)
              return value
docs: Set a value