def test_countby(self):
        parity = _.countBy([1, 2, 3, 4, 5], lambda num, *args: num % 2 not in 0)
        self.assertEqual(parity[True], 2)
        self.assertEqual(parity[False], 3)

        self.assertEqual(_.countBy([1], lambda num, *args: num), 1)

        llist = ["one", "two", "three", "four", "five",
                 "six", "seven", "eight", "nine", "ten"]
        grouped = _.countBy(llist, lambda x, *args: len(x))
        self.assertEqual(grouped[3], 4)
        self.assertEqual(grouped[4], 3)
        self.assertEqual(grouped[5], 3)
dataset/ETHPy150Open serkanyersen/underscore.py/tests/test_collections.py/TestCollections.test_countby/operator `==` -> `not in`