code: func (r *ReadGroup) Get(t Tag) string {
  	switch t {
  	case idTag:
  		return r.Name()
  	case centerTag:
  		return r.center
  	case descriptionTag:
  		return r.description
  	case dateTag:
  		return r.date.Format(iso8601TimeDateN)
  	case flowOrderTag:
  		if r.flowOrder == "" {
  			return "*"
  		}
  		return r.flowOrder
  	case keySequenceTag:
  		return r.keySeq
  	case libraryTag:
  		return r.library
  	case programTag:
  		return r.program
  	case insertSizeTag:
  		return fmt.Sprint(r.insertSize)
  	case platformTag:
  		return r.platform
  	case platformUnitTag:
  		return r.platformUnit
  	case sampleTag:
  		return r.sample
  	}
  	for _, tp := range r.otherTags {
  		if t == tp.tag {
  			return tp.value
  		}
  	}
  	return ""
  }
docs: // Get returns the string representation of the value associated with the
  // given read group line tag. If the tag is not present the empty string is returned.