filters.go
func Repeat(s string, n int) Filter {
	return FilterFunc(func(arg Arg) error {
		for i := 0; i < n; i++ {
			arg.Out <- s
		}
		return nil
	})
}
func Repeat(s string, n int) Filter {
	return FilterFunc(func(arg Arg) error {
		for i := 0; i < n; i++ {
			arg.Out <- s
		}
		return nil
	})
}
// Repeat emits n copies of s.