fix syntax

tests/test_core.py

@@ -13,7 +13,10 @@ from assistant_bot.storage import AssistantStorage
 
 class ReminderParserTests(unittest.TestCase):
     def test_supported_relative_unit(self) -> None:
-        self.assertEqual(unit_to_timedelta(2, "часа").total_seconds(), 7200)
+        delta = unit_to_timedelta(2, "часа")
+        self.assertIsNotNone(delta)
+        assert delta is not None
+        self.assertEqual(delta.total_seconds(), 7200)
 
     def test_absolute_datetime(self) -> None:
         result = parse_reminder(