if stop is not None:
            text = enforce_stop_tokens(text, stop)
        return text
    async def _acall(
        self,
        prompt: str,
        stop: Optional[List[str]] = None,
        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
        **kwargs: Any,
    ) -> str:
        """Async call the Yandex GPT model and return the output.
        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.
        """
        try:
            import asyncio
            import grpc
            from google.protobuf.wrappers_pb2 import DoubleValue, Int64Value
            from yandex.cloud.ai.foundation_models.v1.foundation_models_pb2 import (
                CompletionOptions,
                Message,
            )
            from yandex.cloud.ai.foundation_models.v1.foundation_models_service_pb2 import (  # noqa: E501
                CompletionRequest,
                CompletionResponse,
            )
            from yandex.cloud.ai.foundation_models.v1.foundation_models_service_pb2_grpc import (  # noqa: E501
                TextGenerationAsyncServiceStub,
            )
            from yandex.cloud.operation.operation_service_pb2 import GetOperationRequest
            from yandex.cloud.operation.operation_service_pb2_grpc import (
                OperationServiceStub,
            )
        except ImportError as e:
            raise ImportError(
                "Please install YandexCloud SDK" " with `pip install yandexcloud`."
            ) from e
        operation_api_url = "operation.api.cloud.yandex.net:443"
        channel_credentials = grpc.ssl_channel_credentials()
        async with grpc.aio.secure_channel(self.url, channel_credentials) as channel: