based on: [https://github.com/chujiezheng/chat_templates/blob/main/chat_templates/saiga.jinja]

{% if messages[0]['role'] == 'system' %}
  {% set loop_messages = messages[1:] %}
  {% set system_message = bos_token + 'system' + '
' + messages[0]['content'].strip() + eos_token %}
{% else %}
  {% set loop_messages = messages %}
  {% set system_message = '' %}
{% endif %}

{% for message in loop_messages %}
  {% if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}
      {{ raise_exception('Conversation roles must alternate user/bot/user/bot/...') }}
  {% endif %}

  {% if loop.index0 == 0 %}
      {{ system_message }}
  {% endif %}

  {{ bos_token + message['role'] + '
' + message['content'].strip() + eos_token }}

  {% if loop.last and message['role'] == 'user' and add_generation_prompt %}
      {{ bos_token + 'bot
' }}
  {% endif %}
{% endfor %}
````