docs: function (ev) {
          switch (ev.changedProperty) {
            case 'hasAudio':
              self.audio = ev.newValue
              self.emit('audioChanged', self.audio)
              break
            case 'hasVideo':
              self.video = ev.newValue
              self.emit('videoChanged', self.video)
              break
          }
          self.emit('changed')
        }