langchain/llms/modal.py/Modal/_call
class Modal:    def _call(
        self,
        prompt: str,
        stop: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForLLMRun] = None,
    ) -> str:
        """Call to Modal endpoint."""
        params = self.model_kwargs or {}
        response = requests.post(
            url=self.endpoint_url,
            headers={
                "Content-Type": "application/json",
            },
            json={"prompt": prompt, **params},
        )
        try:
            if prompt in response.json()["prompt"]:
                response_json = response.json()
        except KeyError:
            raise ValueError("LangChain requires 'prompt' key in response.")
        text = response_json["prompt"]
        if stop is not None:
            # I believe this is required since the stop tokens
            # are not enforced by the model parameters
            text = enforce_stop_tokens(text, stop)
        return text