code: func NewDemuxer(t Type, r io.Reader) *Demuxer {
  	max := MaxPackedSize64k
  	if t == Sideband {
  		max = MaxPackedSize
  	}
  
  	return &Demuxer{
  		t:   t,
  		r:   r,
  		max: max,
  		s:   pktline.NewScanner(r),
  	}
  }
docs: // NewDemuxer returns a new Demuxer for the given t and read from r