return splitSeq(s, sep, len(sep))
}

// FieldsSeq returns an iterator over subslices of s split around runs of
// whitespace characters, as defined by [unicode.IsSpace].
// The iterator yields the same subslices that would be returned by [Fields](s),
// but without constructing a new slice containing the subslices.
func FieldsSeq(s []byte) iter.Seq[[]byte] {
	return func(yield func([]byte) bool) {
		start := -1

		if !slices.Equal(result, tt.a) {
			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
			continue
		}

		result2 := sliceOfString(collect(t, FieldsSeq([]byte(tt.s))))
		if !slices.Equal(result2, tt.a) {
			t.Errorf(`collect(FieldsSeq(%q)) = %v; want %v`, tt.s, result2, tt.a)
		}

		if string(b) != tt.s {
			t.Errorf("slice changed to %s; want %s", string(b), tt.s)
		}
		if len(tt.a) > 0 {