code: func (ss *raftSnapshot) Persist(sink raft.SnapshotSink) error {
  	// Write data to sink.
  	if _, err := sink.Write(ss.data); err != nil {
  		sink.Cancel()
  		return err
  	}
  
  	// Close and exit.
  	return sink.Close()
  }
docs: // Persist writes the snapshot to the sink.