@username list in Telegram?

Question

API

I created a private group, drove there who I know, and I need to get the @username of all the participants. In order not to poke each participant and rewrite his username, can this task be blamed on the bot or do it somehow else?
I got the old way on GitHub https://github.com/ypankovych/Telegram-collector where they also give you a file at the end. I can't check because #'access_hash' is stuck:

def get_chat_info(username, client):
    try:
        chat = client(ResolveUsernameRequest(username))
    except UsernameNotOccupiedError:
        print('Chat/channel not found!')
        sys.exit()
    result = {
        'chat_id': -1004460216979,
        'access_hash': chat.chats[0].access_hash
    }
    return result

How to do? If this method works, how to get access_hash.