Add typing_extensions to requirements (#255)

setup.cfg

@@ -28,6 +28,7 @@ zip_safe = False
 python_requires = >=3.7
 install_requires =
     starlette
+    typing_extensions>=4.0;python_version < '3.8'
     jinja2
     sqlalchemy >=1.4, <1.5
     wtforms >=3, <4

sqladmin/forms.py

@@ -1,4 +1,5 @@
 import inspect
+import sys
 from enum import Enum
 from typing import (
     Any,
@@ -20,7 +21,6 @@
 from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession
 from sqlalchemy.orm import ColumnProperty, RelationshipProperty, Session
 from sqlalchemy.sql.schema import Column
-from typing_extensions import Protocol
 from wtforms import (
     BooleanField,
     DateField,
@@ -47,6 +47,11 @@
 )
 from sqladmin.helpers import get_direction, get_primary_key
 
+if sys.version_info >= (3, 8):
+    from typing import Protocol
+else:
+    from typing_extensions import Protocol
+
 
 class Validator(Protocol):
     def __init__(self, *args: Any, **kwargs: Any) -> None: