code: func (manager *impl) GetCheckpoint(checkpointKey string, checkpoint Checkpoint) error {
  	manager.mutex.Lock()
  	defer manager.mutex.Unlock()
  	blob, err := manager.store.Read(checkpointKey)
  	if err != nil {
  		if err == utilstore.ErrKeyNotFound {
  			return errors.ErrCheckpointNotFound
  		}
  		return err
  	}
  	err = checkpoint.UnmarshalCheckpoint(blob)
  	if err == nil {
  		err = checkpoint.VerifyChecksum()
  	}
  	return err
  }
docs: // GetCheckpoint retrieves checkpoint from CheckpointStore.