code: func NewIndentWriter(w io.Writer, pre ...[]byte) io.Writer {
  	return &indentWriter{
  		w:   w,
  		pre: pre,
  		bol: true,
  	}
  }
docs: // NewIndentWriter makes a new write filter that indents the input
  // lines. Each line is prefixed in order with the corresponding
  // element of pre. If there are more lines than elements, the last
  // element of pre is repeated for each subsequent line.