breached in a single  turn, at least in theory. Fortification : In essence, Fortification is the Armor   of the building. Weapons with the quality Wrecking  ignore the Fortification value; other weapons must  first penetrate the Fortification value before damaging  the structure. Abilities with an armor penetrating  effect have no such effect on buildings. Set Buildings on Fire Setting wooden buildings on fire is an often used  tactic during sieges. This requires some kind of  flammable concoction \u2013 it can be an alchemical  grenade, a flaming oil canister or a simple fire made  from dry twigs and tinder. When the building has  been exposed to the flames, a test against  [Cunning  \u2013Fortification]  is rolled to see if it catches fire; if so,  the flames deal 1d4  damage and count as having the quality Wrecking. Note that whoever lights the fire will become the target of ranged attacks, provided that the building in question has windows  or archers on the roof. Those inside a burning building are at risk  of suffering damage each turn the building con - tinues to burn \u2013 a passed Strong  test per turn is Pact-making Beings So, what beings may be  interested in forging a  pact with the charac - ters? In general, they  are creatures of the  categories Beasts,  Undead or Abomina - tions that provide at  least Strong resistance.  A couple of perfect ex - amples of such beings  appear in the adventu - res already published  by J\u00e4rnringen, but since  this is a player\u2019s guide  we cannot specify ex - actly who they are\u2026  106

embed_model = OpenAIEmbedding(embed_batch_size=10)
    llm = OpenAI(model="gpt-3.5-turbo-16k", temperature=0)
    token_counter = TokenCountingHandler(
        tokenizer=tiktoken.encoding_for_model("gpt-3.5-turbo-16k").encode
    )
    callback_manager = CallbackManager([token_counter])
    text_splitter = SentenceSplitter(chunk_size=128, chunk_overlap=15)
    service_context = ServiceContext.from_defaults(
        llm=llm, 
        text_splitter = text_splitter,
        callback_manager=callback_manager, 
        embed_model=embed_model
    )

AttributeError                            Traceback (most recent call last)
Cell In[24], line 3
      1 global chat_engine
----> 3 response = chat_engine.chat("What do you know about Darthus?")

File ~\miniconda3\lib\site-packages\llama_index\core\callbacks\utils.py:41, in trace_method.<locals>.decorator.<locals>.wrapper(self, *args, **kwargs)
     39 callback_manager = cast(CallbackManager, callback_manager)
     40 with callback_manager.as_trace(trace_id):
---> 41     return func(self, *args, **kwargs)

File ~\miniconda3\lib\site-packages\llama_index\core\chat_engine\context.py:160, in ContextChatEngine.chat(self, message, chat_history)
    158 if chat_history is not None:
    159     self._memory.set(chat_history)
--> 160 self._memory.put(ChatMessage(content=message, role="user"))
    162 context_str_template, nodes = self._generate_context(message)
    163 prefix_messages = self._get_prefix_messages_with_context(context_str_template)

File ~\miniconda3\lib\site-packages\llama_index\core\memory\chat_memory_buffer.py:140, in ChatMemoryBuffer.put(self, message)
    138 def put(self, message: ChatMessage) -> None:
    139     """Put chat history."""
--> 140     self.chat_store.add_message(self.chat_store_key, message)

File ~\miniconda3\lib\site-packages\llama_index\core\storage\chat_store\simple_chat_store.py:34, in SimpleChatStore.add_message(self, key, message, idx)
     32 """Add a message for a key."""
     33 if idx is None:
---> 34     self.store.setdefault(key, []).append(message)
     35 else:
     36     self.store.setdefault(key, []).insert(idx, message)

AttributeError: 'ContextChatEngine' object has no attribute 'append'