chore: embrace the 3.12

Author: d-v-b

src/zarr/abc/serializable.py

@@ -1,10 +1,7 @@
-from typing import Protocol, Self, TypeVar
+from typing import Protocol, Self
 
-T_co = TypeVar("T_co", covariant=True)
-T_contra = TypeVar("T_contra", contravariant=True)
 
-
-class JSONSerializable(Protocol[T_contra, T_co]):
+class JSONSerializable[T_contra, T_co](Protocol):
     @classmethod
     def from_json(cls, obj: T_contra) -> Self:
         """