code: func (manager *impl) CreateCheckpoint(checkpointKey string, checkpoint Checkpoint) error {
  	manager.mutex.Lock()
  	defer manager.mutex.Unlock()
  	blob, err := checkpoint.MarshalCheckpoint()
  	if err != nil {
  		return err
  	}
  	return manager.store.Write(checkpointKey, blob)
  }
docs: // CreateCheckpoint persists checkpoint in CheckpointStore.