langchain/llms/openai.py/BaseOpenAI/__new__
class BaseOpenAI:    def __new__(cls, **data: Any) -> Union[OpenAIChat, BaseOpenAI]:  # type: ignore
        """Initialize the OpenAI object."""
        model_name = data.get("model_name", "")
        if model_name.startswith("gpt-3.5-turbo") or model_name.startswith("gpt-4"):
            warnings.warn(
                "You are trying to use a chat model. This way of initializing it is "
                "no longer supported. Instead, please use: "
                "`from langchain.chat_models import ChatOpenAI`"
            )
            return OpenAIChat(**data)
        return super().__new__(cls)