@ApiStatus.ScheduledForRemoval
  @Deprecated
  @Contract(pure = true)
  public static @Unmodifiable @NotNull <T> Set<T> set() {
    return Collections.emptySet();
  }
@ApiStatus.ScheduledForRemoval
  @Deprecated
  @Contract(pure = true)
  public static @Unmodifiable @NotNull <T> Set<T> set()