refac: modernize imports, standardize type hints and docstrings

backend/open_webui/retrieval/web/serpstack.py

@@ -1,17 +1,17 @@
+from __future__ import annotations
+
 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_serpstack(
     api_key: str,
     query: str,
     count: int,
-    filter_list: Optional[list[str]] = None,
+    filter_list: list[str | None] = None,
     https_enabled: bool = True,
 ) -> list[SearchResult]:
     """Search using serpstack.com's and return the results as a list of SearchResult objects.