Inconsistency of prompt for llama2

[XuHwang]

As described in https://huggingface.co/blog/codellama#conversational-instructions, the data format of conversations are formatted as follows:

<s>[INST] <<SYS>>
{{ system_prompt }}
<</SYS>>

{{ user_msg_1 }} [/INST] {{ model_answer_1 }} </s><s>[INST] {{ user_msg_2 }} [/INST]

Here, <s> is put at the beginning of the prompt. While in the line 1113 of fschat/conversation.py, the <s> is omitted in the system_template. Is the omission correct or just a bug?

[hlmu]

Seems this piece of code is used along with transformers.LlamaTokenizer with add_prefix_space=True by default, which will prepend an extra <s>.