code: func ReadTagged(text, sep string) TupleSlice {
  	t := TupleSlice{}
  	for _, sent := range strings.Split(text, "\n") {
  		tokens := []string{}
  		tags := []string{}
  		for _, token := range strings.Split(sent, " ") {
  			parts := strings.Split(token, sep)
  			tokens = append(tokens, parts[0])
  			tags = append(tags, parts[1])
  		}
  		t = append(t, [][]string{tokens, tags})
  	}
  	return t
  }
docs: // ReadTagged converts pre-tagged input into a TupleSlice suitable for training.