How to use the inflect.BadNumValueError function in inflect

p.num()
        ret = p.num("3")
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, "3")

        p.num()
        ret = p.num(count=3, show=1)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, "3")

        p.num()
        ret = p.num(count=3, show=0)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, "")

        self.assertRaises(BadNumValueError, p.num, "text")

p.num()
        ret = p.num("3")
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '3')

        p.num()
        ret = p.num(count=3, show=1)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '3')

        p.num()
        ret = p.num(count=3, show=0)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '')

        self.assertRaises(BadNumValueError, p.num, 'text')

p.num()
        ret = p.num("3")
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '3')

        p.num()
        ret = p.num(count=3, show=1)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '3')

        p.num()
        ret = p.num(count=3, show=0)
        self.assertEqual(p.persistent_count, 3)
        self.assertEqual(ret, '')

        self.assertRaises(BadNumValueError, p.num, 'text')

def num(self, count=None, show=None):  # (;$count,$show)
        """
        Set the number to be used in other method calls.

        Returns count.

        Set show to False to return '' instead.

        """
        if count is not None:
            try:
                self.persistent_count = int(count)
            except ValueError:
                raise BadNumValueError
            if (show is None) or show:
                return str(count)
        else:
            self.persistent_count = None
        return ""