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

        FPTree tree = FPTree.of(20, () -> ItemSetTestData.read("transaction/pima.D38.N768.C2"));
        assertEquals(1803, FPGrowth.apply(tree).count());
    }