fix: wsgiref.types not available in python 3.10

Author: Jens Kürten

csfunctions/devserver.py

@@ -35,13 +35,17 @@
 import os
 import time
 from collections.abc import Iterable
-from wsgiref.types import StartResponse, WSGIEnvironment
+from typing import TYPE_CHECKING
 
 from werkzeug.serving import run_simple
 from werkzeug.wrappers import Request, Response
 
 from csfunctions.handler import FunctionNotRegistered, execute
 
+if TYPE_CHECKING:
+    # these annotations are not available in python 3.10
+    from wsgiref.types import StartResponse, WSGIEnvironment
+
 
 def _is_error_response(function_response: str | dict):
     """