docs/langchain/libs/community/langchain_community/chat_models/meta.py

from typing import List

from langchain_core.messages import (
    AIMessage,
    BaseMessage,
    ChatMessage,
    HumanMessage,
    SystemMessage,
)


def _convert_one_message_to_text_llama(message: BaseMessage) -> str:
    if isinstance(message, ChatMessage):
        message_text = f"\n\n{message.role.capitalize()}: {message.content}"
    elif isinstance(message, HumanMessage):
        message_text = f"[INST] {message.content} [/INST]"
    elif isinstance(message, AIMessage):
        message_text = f"{message.content}"
    elif isinstance(message, SystemMessage):
        message_text = f"<<SYS>> {message.content} <</SYS>>"
    else:
        raise ValueError(f"Got unknown type {message}")
    return message_text


def convert_messages_to_prompt_llama(messages: List[BaseMessage]) -> str:
    """Convert a list of messages to a prompt for llama."""

    return "\n".join(
        [_convert_one_message_to_text_llama(message) for message in messages]
    )