interfaces: fix get_interface_attr typing (commaai#30813)

* fix

* Update selfdrive/car/interfaces.py

selfdrive/car/interfaces.py

@@ -3,6 +3,7 @@
 import numpy as np
 import tomllib
 from abc import abstractmethod, ABC
+from enum import StrEnum
 from typing import Any, Dict, Optional, Tuple, List, Callable
 
 from cereal import car
@@ -440,7 +441,7 @@ def get_loopback_can_parser(CP):
 
 # interface-specific helpers
 
-def get_interface_attr(attr: str, combine_brands: bool = False, ignore_none: bool = False) -> Dict[str, Any]:
+def get_interface_attr(attr: str, combine_brands: bool = False, ignore_none: bool = False) -> Dict[str | StrEnum, Any]:
   # read all the folders in selfdrive/car and return a dict where:
   # - keys are all the car models or brand names
   # - values are attr values from all car folders