else:
                # use default credentials
                session = boto3.Session()
            client_params = {}
            if values.get("region_name"):
                client_params["region_name"] = values["region_name"]
            values["client"] = session.client("comprehend", **client_params)
            return values
        except ImportError:
            raise ModuleNotFoundError(
                "Could not import boto3 python package. "
                "Please install it with `pip install boto3`."
            )
        except Exception as e:
            raise ValueError(
                "Could not load credentials to authenticate with AWS client. "
                "Please check that credentials in the specified "
                "profile name are valid."
            ) from e
    @property
    def output_keys(self) -> List[str]:
        """
        Returns a list of output keys.
        This method defines the output keys that will be used to access the output
        values produced by the chain or function. It ensures that the specified keys
        are available to access the outputs.
        Returns:
            List[str]: A list of output keys.
        Note:
            This method is considered private and may not be intended for direct
            external use.
        """
        return [self.output_key]
    @property
    def input_keys(self) -> List[str]:
        """
        Returns a list of input keys expected by the prompt.
        This method defines the input keys that the prompt expects in order to perform
        its processing. It ensures that the specified keys are available for providing
        input to the prompt.
        Returns:
            List[str]: A list of input keys.
        Note:
            This method is considered private and may not be intended for direct
            external use.
        """
        return [self.input_key]
    def _call(