@Contract(pure = true)
  public static int indexOf(@NotNull CharSequence sequence, @NotNull CharSequence infix, int start, int end) {
    for (int i = start; i <= end - infix.length(); i++) {
      if (startsWith(sequence, i, infix)) {
        return i;
      }
    }
    return -1;
  }
@Contract(pure = true)
  public static int indexOf(@NotNull CharSequence sequence, @NotNull CharSequence infix, int start, int end)