Первый полностью рабочий функционал

filters/__init__.py

@@ -1,9 +1,9 @@
 from aiogram import Dispatcher
 
 from loader import dp
-# from .is_admin import AdminFilter
+from .group_chat import IsGroup
 
 
 if __name__ == "filters":
-    # dp.filters_factory.bind(AdminFilter)
+    dp.filters_factory.bind(IsGroup)
     pass

filters/group_chat.py

@@ -0,0 +1,9 @@
+from aiogram import types
+from aiogram.dispatcher.filters import BoundFilter
+
+class IsGroup(BoundFilter):
+    async def check(self, message: types.Message) -> bool:
+        return message.chat.type in (
+            types.ChatType.GROUP,
+            types.ChatType.SUPERGROUP
+        )