code: def time_left(self):
          
          if self._timestamp is None:
              return 0
          else:
              time_left = self.timeout - (time.time() - self._timestamp)
              return time_left if time_left > 0 else 0
docs: `int`: The amount of time left until the subscription expires (seconds)
  
          If the subscription is unsubscribed (or not yet subscribed),
          `time_left` is 0.