code: def event_channels_happened(self, eventcode):
          
          ret = self.command(
              'eventManager.cgi?action=getEventIndexes&code={0}'.format(
                  eventcode)
          )
          return ret.content.decode('utf-8')
docs: Params:
  
          VideoMotion: motion detection event
          VideoLoss: video loss detection event
          VideoBlind: video blind detection event
          AlarmLocal: alarm detection event
          StorageNotExist: storage not exist event
          StorageFailure: storage failure event
          StorageLowSpace: storage low space event
          AlarmOutput: alarm output event