langchain/llms/writer.py/Writer/_call
class Writer:    def _call(
        self,
        prompt: str,
        stop: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForLLMRun] = None,
    ) -> str:
        """Call out to Writer's completions endpoint.

        Args:
            prompt: The prompt to pass into the model.
            stop: Optional list of stop words to use when generating.

        Returns:
            The string generated by the model.

        Example:
            .. code-block:: python

                response = Writer("Tell me a joke.")
        """
        if self.base_url is not None:
            base_url = self.base_url
        else:
            base_url = (
                "https://enterprise-api.writer.com/llm"
                f"/organization/{self.writer_org_id}"
                f"/model/{self.model_id}/completions"
            )

        response = requests.post(
            url=base_url,
            headers={
                "Authorization": f"{self.writer_api_key}",
                "Content-Type": "application/json",
                "Accept": "application/json",
            },
            json={"prompt": prompt, **self._default_params},
        )
        text = response.text
        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