code: func (tag *Tag) Size() int {
  	if !tag.HasFrames() {
  		return 0
  	}
  
  	var n int
  	n += tagHeaderSize // Add the size of tag header
  	tag.iterateOverAllFrames(func(id string, f Framer) error {
  		n += frameHeaderSize + f.Size() // Add the whole frame size
  		return nil
  	})
  
  	return n
  }
docs: // Size returns the size of tag (tag header + size of all frames) in bytes.