code: func (as AnnotatedSentence) Labels() []DependencyType {
  	retVal := make([]DependencyType, len(as))
  	for i, a := range as {
  		retVal[i] = a.DependencyType
  	}
  	return retVal
  }
docs: // Labels returns the DependencyTypes of the sentence. The return value has exactly the same length as the sentence.