async fn evaluate_expression(
        &self,
        input: EvaluateExpressionInput,
    ) -> Result<EvaluateExpressionOutput, RusotoError<EvaluateExpressionError>> {
        let mut request = self.new_signed_request("POST", "/");
        request.add_header("x-amz-target", "DataPipeline.EvaluateExpression");
        let encoded = serde_json::to_string(&input).unwrap();
        request.set_payload(Some(encoded));

        let response = self
            .sign_and_dispatch(request, EvaluateExpressionError::from_response)
            .await?;
        let mut response = response;
        let response = response.buffer().await.map_err(RusotoError::HttpDispatch)?;
        proto::json::ResponsePayload::new(&response).deserialize::<EvaluateExpressionOutput, _>()
    }
<p>Task runners call <code>EvaluateExpression</code> to evaluate a string in the context of the specified object. For example, a task runner can evaluate SQL queries stored in Amazon S3.</p>
rusoto/services/datapipeline/src/generated.rs