fixup! WIP descriptors

src/property_utils/units/descriptors.py

@@ -9,7 +9,13 @@
 """
 
 from enum import Enum, EnumMeta
-from typing import List, Union, Protocol, TypeAlias, Optional, TypeVar
+from typing import List, Union, Protocol, Optional, TypeVar
+
+try:
+    from typing import TypeAlias  # Python >= 3.10
+except ImportError:
+    from typing_extensions import TypeAlias  # Python < 3.10
+
 from dataclasses import dataclass, field
 
 from property_utils.exceptions.exceptions import (