Arguments

When you declare the rules with typed parameters, Folds provides the arguments automatically:

• str: gets the current message text
• Message or SystemMessage (or another Telethon event): gets the current event
• ThisReplyTo: resolves the message which this message replies to
• ThisChat: resolves the current chat
• ThisSender: resolves the current sender
• ThisInputChat: resolves the current Telethon input chat
• ThisInputSender: resolves the current Telethon input sender

Example

@bot.group_message()
async def f(chat: ThisChat):
    # Now, Telethon has resolved the chat even if 
    # the chat info didn't come with the update 
    return f'I got a message from {chat.title}'

If rewritten without ThisChat, the code becomes:

@bot.group_message()
async def f(message: Message):
    chat = await message.get_chat()
    return f'I got a message from {chat.title}'