Update src/pendulum/interval.py

Author: ashb

src/pendulum/interval.py

@@ -6,7 +6,7 @@
 from datetime import date
 from datetime import datetime
 from datetime import timedelta
-from typing import TYPE_CHECKING, Any, Union, cast, overload
+from typing import TYPE_CHECKING, Any, Generic, TypeVar, cast, overload
 
 import pendulum