public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {
    return ofClassAndContents(Object.class, (E[]) new Object[0], Arrays.asList(contents));
  }

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> from(Collection<? extends E> contents) {
    return ofClassAndContents(Object.class, (E[]) new Object[0], contents);
  }

  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {
    return ofClassAndContents(Object.class, (E[]) new Object[0], Arrays.asList(contents));
  }

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> from(Collection<? extends E> contents) {
    return ofClassAndContents(Object.class, (E[]) new Object[0], contents);
  }

    return new MinimalCollection<>(Object.class, true, contents);
  }

  // TODO: use this
  public static <E extends @Nullable Object> MinimalCollection<E> ofClassAndContents(
      Class<? super @NonNull E> type, E... contents) {
    return new MinimalCollection<>(type, true, contents);
  }

  private final E[] contents;
  private final Class<? super @NonNull E> type;

    return new MinimalCollection<>(Object.class, true, contents);
  }

  // TODO: use this
  public static <E extends @Nullable Object> MinimalCollection<E> ofClassAndContents(
      Class<? super @NonNull E> type, E... contents) {
    return new MinimalCollection<>(type, true, contents);
  }

  private final E[] contents;
  private final Class<? super @NonNull E> type;