langchain/prompts/chat.py/ChatPromptTemplate/from_role_strings
class ChatPromptTemplate:    def from_role_strings(
        cls, string_messages: List[Tuple[str, str]]
    ) -> ChatPromptTemplate:
        messages = [
            ChatMessagePromptTemplate(
                prompt=PromptTemplate.from_template(template), role=role
            )
            for role, template in string_messages
        ]
        return cls.from_messages(messages)