code: func WithCluster(c map[string]lingo.Cluster) ConsOpt {
  	fn := func(p *Tagger) {
  		p.clusters = c
  	}
  	return fn
  }
docs: // WithCluster creates a *Tagger with a brown cluster corpus (a map of strings to the brown clusters).
  // If no brown cluster corpus was passed in, the cluster won't be set, and the POSTagger will be less accurate