Partial fix for mypy issues

webserver/handlers/api/dxstats.py

@@ -37,8 +37,9 @@ class APIDxStatsHandler(tornado.web.RequestHandler):
 
     def get(self) -> None:
         try:
+            assert self._spots is not None, "initialize() must be called before get()"
             one_hour_ago = (datetime.now(pytz.UTC) - timedelta(hours=1)).timestamp()
-            counts = Counter()
+            counts: Counter[tuple[str, str, str]] = Counter()
 
             for key in self._spots.keys():  # noqa: SIM118
                 spot = self._spots.get(key)