@Contract(pure = true)
  public static @NotNull String repeat(@NotNull String s, int count) {
    if (count == 0) return "";
    assert count >= 0 : count;
    StringBuilder sb = new StringBuilder(s.length() * count);
    for (int i = 0; i < count; i++) {
      sb.append(s);
    }
    return sb.toString();
  }
@Contract(pure = true)
  public static @NotNull String repeat(@NotNull String s, int count)