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: start_lexer.go
    path of file: ./repos/dep-tree/internal/python/python_grammar
    
    the code of the file until where you have to start completion: package python_grammar

// This wraps a lexer so that it includes a SOF token with the start of the
    
func LexerWithSOF(parent lexer.Definition) lexer.Definition {
	out := maps.Clone(parent.Symbols())
	if _, ok := out["SOF"]; ok {
		panic("Wrapped lexer should not have the SOF token")
	}
	next := lexer.TokenType(-1)
	for _, t := range out {
		if t <= next {
			next = t - 1
		}
	}
	out["SOF"] = next - 1
	return &startLexerDef{parent: parent, symbols: out}
}