@SafeVarargs
  @Contract(pure = true)
  @Deprecated
  public static @Unmodifiable @NotNull <E> Set<E> immutableSet(E @NotNull ... elements) {
    switch (elements.length) {
      case 0:
        return Collections.emptySet();
      case 1:
        return Collections.singleton(elements[0]);
      default:
        //noinspection SSBasedInspection
        return Collections.unmodifiableSet(new HashSet<>(Arrays.asList(elements)));
    }
  }
@SafeVarargs
  @Contract(pure = true)
  @Deprecated
  public static @Unmodifiable @NotNull <E> Set<E> immutableSet(E @NotNull ... elements)