code: func decorate(call _entry, s string) string {
  
  	file, line := call.File, call.Line
  	if call.PC > 0 {
  		// Truncate file name at last file name separator.
  		if index := strings.LastIndex(file, "/"); index >= 0 {
  			file = file[index+1:]
  		} else if index = strings.LastIndex(file, "\\"); index >= 0 {
  			file = file[index+1:]
  		}
  	} else {
  		file = "???"
  		line = 1
  	}
  	buf := new(bytes.Buffer)
  	// Every line is indented at least one tab.
  	buf.WriteByte('\t')
  	fmt.Fprintf(buf, "%s:%d: ", file, line)
  	lines := strings.Split(s, "\n")
  	if l := len(lines); l > 1 && lines[l-1] == "" {
  		lines = lines[:l-1]
  	}
  	for i, line := range lines {
  		if i > 0 {
  			// Second and subsequent lines are indented an extra tab.
  			buf.WriteString("\n\t\t")
  		}
  		buf.WriteString(line)
  	}
  	buf.WriteByte('\n')
  	return buf.String()
  }
docs: // decorate prefixes the string with the file and line of the call site
  // and inserts the final newline if needed and indentation tabs for formascing.