class chat_history: def __init__(self, storage_dir="chat_histories"): self.storage_dir = storage_dir self.user_histories = {} os.makedirs(self.storage_dir, exist_ok=True) def login(self, username): self.username = username self.user_histories[username] = self._load_history(username) def add_message(self, role, content): if not hasattr(self, "use..