refac: modernize imports, standardize type hints and docstrings

backend/open_webui/retrieval/web/serper.py

@@ -1,14 +1,14 @@
+from __future__ import annotations
+
 import json
 import logging
-from typing import Optional
 
 import requests
 from open_webui.retrieval.web.main import SearchResult, get_filtered_results
 
 log = logging.getLogger(__name__)
 
-
-def search_serper(api_key: str, query: str, count: int, filter_list: Optional[list[str]] = None) -> list[SearchResult]:
+def search_serper(api_key: str, query: str, count: int, filter_list: list[str | None] = None) -> list[SearchResult]:
     """Search using serper.dev's API and return the results as a list of SearchResult objects.
 
     Args: