args.go
func (a *Args) VisitAll(f func(key, value []byte)) {
	visitArgs(a.args, f)
}
func (a *Args) VisitAll(f func(key, value []byte)) {
	visitArgs(a.args, f)
}
// VisitAll calls f for each existing arg.
//
// f must not retain references to key and value after returning.
// Make key and/or value copies if you need storing them after returning.