Fixed optional annotation

src/ephys_link/server.py

@@ -9,6 +9,8 @@
 4. Relay the response from :mod:`ephys_link.sensapex_handler` to the callback function
 """
 
+from __future__ import annotations
+
 import json
 import sys
 from signal import SIGINT, SIGTERM, signal
@@ -354,7 +356,7 @@ async def catch_all(_, __, data: Any) -> str:
         print(f"[UNKNOWN EVENT]:\t {data}")
         return "UNKNOWN_EVENT"
 
-    def launch(self, platform_type: str, server_port: int, pathfinder_port: int = None) -> None:
+    def launch(self, platform_type: str, server_port: int, pathfinder_port: int | None = None) -> None:
         """Launch the server.
 
         :param platform_type: Parsed argument for platform type.