code: def major_service_class(self):
          
          major_service = []
          for i in BTCoD._MAJOR_SERVICE_CLASS.keys():
              if (self.cod & i):
                  major_service.append(BTCoD._MAJOR_SERVICE_CLASS[i])
          return major_service
docs: Return the major service class property decoded e.g.,
          Audio, Telephony, etc