code: def update_event(self, event, action, flags):
          
          if action == PYCBC_EVACTION_UNWATCH:
              if event.flags & LCB_READ_EVENT:
                  self.reactor.removeReader(event)
              if event.flags & LCB_WRITE_EVENT:
                  self.reactor.removeWriter(event)
  
          elif action == PYCBC_EVACTION_WATCH:
              if flags & LCB_READ_EVENT:
                  self.reactor.addReader(event)
              if flags & LCB_WRITE_EVENT:
                  self.reactor.addWriter(event)
  
              if flags & LCB_READ_EVENT == 0:
                  self.reactor.removeReader(event)
              if flags & LCB_WRITE_EVENT == 0:
                  self.reactor.removeWriter(event)
docs: Called by libcouchbase to add/remove event watchers