public static Stream<ItemSet> apply(FPTree tree) {
        FPGrowth growth = new FPGrowth(tree);
        return StreamSupport.stream(growth.spliterator(), false);
    }
@Test
    public void testKosarak() {
        System.out.println("kosarak");

        FPTree tree = FPTree.of(1500, () -> ItemSetTestData.read("transaction/kosarak.dat"));
        assertEquals(219725, FPGrowth.apply(tree).count());
    }