code: func (tag *Tag) AddFrame(id string, f Framer) {
  	if id == "" || f == nil {
  		return
  	}
  
  	if mustFrameBeInSequence(id) {
  		sequence := tag.sequences[id]
  		if sequence == nil {
  			sequence = getSequence()
  		}
  		sequence.AddFrame(f)
  		tag.sequences[id] = sequence
  	} else {
  		tag.frames[id] = f
  	}
  }
docs: // AddFrame adds f to tag with appropriate id. If id is "" or f is nil,
  // AddFrame will not add it to tag.
  //
  // If you want to add attached picture, comment or unsynchronised lyrics/text
  // transcription frames, better use AddAttachedPicture, AddCommentFrame
  // or AddUnsynchronisedLyricsFrame methods respectively.