code: def ProduceEventSource(self, event_source):
      
      if not self._storage_writer:
        raise RuntimeError('Storage writer not set.')
  
      self._storage_writer.AddEventSource(event_source)
      self._number_of_event_sources += 1
  
      self.last_activity_timestamp = time.time()
docs: Produces an event source.
  
      Args:
        event_source (EventSource): an event source.
  
      Raises:
        RuntimeError: when storage writer is not set.