Fix typing for Python 3.10.

src/codehelp/context.py

@@ -8,7 +8,7 @@
 
 from flask import current_app
 from jinja2 import Environment
-from typing_extensions import Self
+from typing_extensions import Self  # for 3.10
 from werkzeug.datastructures import ImmutableMultiDict
 
 from gened.auth import get_auth

src/gened/app_data.py

@@ -7,10 +7,11 @@
 from copy import deepcopy
 from dataclasses import dataclass, field
 from sqlite3 import Cursor, Row
-from typing import Final, Protocol, Self
+from typing import Final, Protocol
 from urllib.parse import urlencode
 
 from flask import flash, request
+from typing_extensions import Self  # for 3.10
 
 from gened.tables import DataTable