Invokes the lambda function and returns the
        result.
        Args:
            query: an input to passed to the lambda
                function as the ``body`` of a JSON
                object.
        """  # noqa: E501
        res = self.lambda_client.invoke(
            FunctionName=self.function_name,
            InvocationType="RequestResponse",
            Payload=json.dumps({"body": query}),
        )
        try:
            payload_stream = res["Payload"]
            payload_string = payload_stream.read().decode("utf-8")
            answer = json.loads(payload_string)["body"]
        except StopIteration:
            return "Failed to parse response from Lambda"
        if answer is None or answer == "":
            # We don't want to return the assumption alone if answer is empty
            return "Request failed."
        else:
            return f"Result: {answer}"