code: def GetNumberOfEventSources(self):
      
      number_of_event_sources = self._CountStoredAttributeContainers(
          self._CONTAINER_TYPE_EVENT_SOURCE)
  
      number_of_event_sources += self._GetNumberOfSerializedAttributeContainers(
          self._CONTAINER_TYPE_EVENT_SOURCE)
      return number_of_event_sources
docs: Retrieves the number event sources.
  
      Returns:
        int: number of event sources.