code: func (api *PublicFilterAPI) timeoutLoop() {
  	ticker := time.NewTicker(5 * time.Minute)
  	for {
  		<-ticker.C
  		api.filtersMu.Lock()
  		for id, f := range api.filters {
  			select {
  			case <-f.deadline.C:
  				f.s.Unsubscribe()
  				delete(api.filters, id)
  			default:
  				continue
  			}
  		}
  		api.filtersMu.Unlock()
  	}
  }
docs: // timeoutLoop runs every 5 minutes and deletes filters that have not been recently used.
  // Tt is started when the api is created.