add initial bits of typechecking

webscraper.py

@@ -1,5 +1,5 @@
 import requests
-from ratelimit import limits, sleep_and_retry
+from ratelimit import limits, sleep_and_retry  # type: ignore
 from src.database import Database
 import xml.etree.ElementTree as ET
 
@@ -9,7 +9,7 @@ db = Database("lfer.db")
 
 @sleep_and_retry
 @limits(calls=10, period=1)
-def fetch_data(ppn):
+def fetch_data(ppn: str):
     api_url = f"https://sru.bsz-bw.de/swb?version=1.1&query=pica.ppn%3D{ppn}&operation=searchRetrieve&maximumRecords=10&recordSchema=marcxmlk10os"
     response = requests.get(api_url)
     return response.text