async fn start_lifecycle_policy_preview(
        &self,
        input: StartLifecyclePolicyPreviewRequest,
    ) -> Result<StartLifecyclePolicyPreviewResponse, RusotoError<StartLifecyclePolicyPreviewError>>
    {
        let mut request = self.new_signed_request("POST", "/");
        request.add_header(
            "x-amz-target",
            "AmazonEC2ContainerRegistry_V20150921.StartLifecyclePolicyPreview",
        );
        let encoded = serde_json::to_string(&input).unwrap();
        request.set_payload(Some(encoded));

        let response = self
            .sign_and_dispatch(request, StartLifecyclePolicyPreviewError::from_response)
            .await?;
        let mut response = response;
        let response = response.buffer().await.map_err(RusotoError::HttpDispatch)?;
        proto::json::ResponsePayload::new(&response)
            .deserialize::<StartLifecyclePolicyPreviewResponse, _>()
    }
<p>Starts a preview of a lifecycle policy for the specified repository. This allows you to see the results before associating the lifecycle policy with the repository.</p>
rusoto/services/ecr/src/generated.rs