Use Dict[] instead of dict[]

Author: Natarajan Krishnaswami

tests/test_attribute_keyed_dict.py

@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Optional
+from typing import Dict, Optional
 
 from sqlalchemy.orm.collections import attribute_keyed_dict
 from sqlmodel import Field, Index, Relationship, Session, SQLModel, create_engine
@@ -25,7 +25,7 @@ class Parent(SQLModel, table=True):
         __tablename__ = "parents"
 
         id: Optional[int] = Field(primary_key=True, default=None)
-        children_by_color: dict[Color, Child] = Relationship(
+        children_by_color: Dict[Color, Child] = Relationship(
             sa_relationship_kwargs={"collection_class": attribute_keyed_dict("color")}
         )