code: func (builder *SSMLTextBuilder) AppendPartOfSpeech(role WordRole, text string) *SSMLTextBuilder {
  
  	if role != "" {
  		builder.buffer.WriteString(fmt.Sprintf("<w role=\"%s\">%s</w>", role, text))
  	}
  
  	return builder
  }
docs: // AppendPartOfSpeech is used to explictily define the part of speech for a word that is being
  // appended to the text to speech output sent in a skill server response.