code: def commit(self):
          
          assert self.batch is not None, "No active batch, call start() first"
  
          logger.debug("Comitting batch from %d sources...", len(self.batch))
  
          # Determine item priority.
          by_priority = []
          for name in self.batch.keys():
              priority = self.priorities.get(name, self.default_priority)
              by_priority.append((priority, name))
  
          for priority, name in sorted(by_priority, key=lambda key: key[0]):
              logger.debug("Processing items from '%s' (priority=%d)...", name, priority)
              items = self.batch[name]
              for handlers in items.values():
                  for agg, handler in handlers:
                      try:
                          if agg is None:
                              handler()
                          else:
                              handler(agg)
                      except Exception as error:
                          # Log errors and proceed to evaluate the next handler.
                          logger.exception("Error while invoking handler.")
  
          self.batch = None
  
          logger.debug("Batch committed.")
docs: Commit a batch.