[py] PEP 484 type hints for selenium.webdriver.remote.file_detector (#9606)

Signed-off-by: oleg.hoefling <oleg.hoefling@gmail.com>

Co-authored-by: David Burns <david.burns@theautomatedtester.co.uk>

Author: hoefling

py/selenium/webdriver/remote/file_detector.py

@@ -17,7 +17,9 @@
 
 from abc import ABCMeta, abstractmethod
 import os
+from typing import Optional
 from selenium.webdriver.common.utils import keys_to_typing
+from selenium.types import AnyKey
 
 
 class FileDetector(metaclass=ABCMeta):
@@ -27,16 +29,16 @@ class FileDetector(metaclass=ABCMeta):
     """
 
     @abstractmethod
-    def is_local_file(self, *keys):
-        return
+    def is_local_file(self, *keys: AnyKey) -> Optional[str]:
+        return None
 
 
 class UselessFileDetector(FileDetector):
     """
     A file detector that never finds anything.
     """
 
-    def is_local_file(self, *keys):
+    def is_local_file(self, *keys: AnyKey) -> Optional[str]:
         return None
 
 
@@ -45,7 +47,7 @@ class LocalFileDetector(FileDetector):
     Detects files on the local disk.
     """
 
-    def is_local_file(self, *keys):
+    def is_local_file(self, *keys: AnyKey) -> Optional[str]:
         file_path = ''.join(keys_to_typing(keys))
 
         if not file_path: