code: func (w *indentWriter) Write(p []byte) (n int, err error) {
  	for _, c := range p {
  		if w.bol {
  			var i int
  			i, err = w.w.Write(w.pre[w.sel][w.off:])
  			w.off += i
  			if err != nil {
  				return n, err
  			}
  		}
  		_, err = w.w.Write([]byte{c})
  		if err != nil {
  			return n, err
  		}
  		n++
  		w.bol = c == '\n'
  		if w.bol {
  			w.off = 0
  			if w.sel < len(w.pre)-1 {
  				w.sel++
  			}
  		}
  	}
  	return n, nil
  }
docs: // The only errors returned are from the underlying indentWriter.