You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: sppf.go
    path of file: ./repos/gogll/sppf
    
    the code of the file until where you have to start completion: // Package sppf is generated by gogll. Do not edit.

/*
Package sppf implements a Shared Packed Parse Forest as defined in:

	Elizabeth Scott, Adrian Johnstone
	GLL parse-tree generation

    
func slotString(nt symbols.NT, body symbols.Symbols, pos int) string {
	w := new(bytes.Buffer)
	fmt.Fprintf(w, "%s:", nt)
	for i, sym := range body {
		fmt.Fprint(w, " ")
		if i == pos {
			fmt.Fprint(w, "•")
		}
		fmt.Fprint(w, sym)
	}
	if len(body) == pos {
		fmt.Fprint(w, "•")
	}
	return w.String()
}