Typing for handlers and add hello world to index page of docs

aiogram/dispatcher/handler/base.py

@@ -6,11 +6,17 @@ from aiogram.api.types import TelegramObject
 
 
 class BaseHandlerMixin:
+    """
+    Typed mixin. Do nothing.
+    """
     event: TelegramObject
     data: Dict[str, Any]
 
 
 class _HandlerBotMixin(BaseHandlerMixin):
+    """
+    Mixin adds bot attribute
+    """
     @property
     def bot(self) -> Bot:
         if "bot" in self.data:
@@ -19,7 +25,9 @@ class _HandlerBotMixin(BaseHandlerMixin):
 
 
 class BaseHandler(_HandlerBotMixin, ABC):
-    event: TelegramObject
+    """
+    Base class for all class-based handlers
+    """
 
     def __init__(self, event: TelegramObject, **kwargs: Any) -> None:
         self.event = event

aiogram/dispatcher/handler/message.py

@@ -1,7 +1,7 @@
 from abc import ABC
 from typing import Optional
 
-from aiogram.api.types import Message
+from aiogram.api.types import Message, User, Chat
 from aiogram.dispatcher.filters import CommandObject
 from aiogram.dispatcher.handler.base import BaseHandler, BaseHandlerMixin
 
@@ -10,11 +10,11 @@ class MessageHandler(BaseHandler, ABC):
     event: Message
 
     @property
-    def from_user(self):
+    def from_user(self) -> User:
         return self.event.from_user
 
     @property
-    def chat(self):
+    def chat(self) -> Chat:
         return self.event.chat