code: func (p *Tagger) Stem(a string) (string, error) {
  	if p.Stemmer == nil {
  		return "", componentUnavailable("stemmer")
  	}
  	return p.Stemmer.Stem(a)
  }
docs: // Stem implements the lingo.Stemmer interface. It however, defers the actual stemming to the stemmer passed in.