code: def process_tick(self, tup):
      
      curtime = int(time.time())
      window_info = WindowContext(curtime - self.window_duration, curtime)
      self.processWindow(window_info, list(self.current_tuples))
      for tup in self.current_tuples:
        self.ack(tup)
      self.current_tuples.clear()
docs: Called every window_duration