a := make([][]byte, len(spans))
	for i, span := range spans {
		a[i] = s[span.start:span.end:span.end]
	}

	return a
}

// Join concatenates the elements of s to create a new byte slice. The separator
// sep is placed between elements in the resulting slice.
func Join(s [][]byte, sep []byte) []byte {
	if len(s) == 0 {
		return []byte{}
	}
	if len(s) == 1 {
		// Just return a copy.