code: @NotNull
  	public static Promise<Void> sequence(@NotNull AsyncSupplier<Void> promise1, @NotNull AsyncSupplier<Void> promise2) {
  		return promise1.get().then($ -> sequence(promise2));
  	}
docs: Gets {@code Promise}s from provided {@code AsyncSupplier}s,
  end executes them consequently, discarding their results.