code: func parseCheckpoints(checkpointStrings []string) ([]chaincfg.Checkpoint, error) {
  	if len(checkpointStrings) == 0 {
  		return nil, nil
  	}
  	checkpoints := make([]chaincfg.Checkpoint, len(checkpointStrings))
  	for i, cpString := range checkpointStrings {
  		checkpoint, err := newCheckpointFromStr(cpString)
  		if err != nil {
  			return nil, err
  		}
  		checkpoints[i] = checkpoint
  	}
  	return checkpoints, nil
  }
docs: // parseCheckpoints checks the checkpoint strings for valid syntax
  // ('<height>:<hash>') and parses them to chaincfg.Checkpoint instances.