Minor typing fix

main.py

@@ -16,7 +16,7 @@ if __name__ == "__main__":
     import traceback
     import tkinter as tk
     from tkinter import messagebox
-    from typing import IO, NoReturn
+    from typing import NoReturn, TYPE_CHECKING
 
     import truststore
     truststore.inject_into_ssl()
@@ -29,6 +29,9 @@ if __name__ == "__main__":
     from utils import lock_file, resource_path, set_root_icon
     from constants import LOGGING_LEVELS, SELF_PATH, FILE_FORMATTER, LOG_PATH, LOCK_PATH
 
+    if TYPE_CHECKING:
+        from _typeshed import SupportsWrite
+
     warnings.simplefilter("default", ResourceWarning)
 
     if sys.version_info < (3, 10):
@@ -39,7 +42,7 @@ if __name__ == "__main__":
             super().__init__(*args, **kwargs)
             self._message: io.StringIO = io.StringIO()
 
-        def _print_message(self, message: str, file: IO[str] | None = None) -> None:
+        def _print_message(self, message: str, file: SupportsWrite[str] | None = None) -> None:
             self._message.write(message)
             # print(message, file=self._message)