Upon success, returns an empty response. Otherwise, throws an exception.
Inheritance: Amazon.Runtime.AmazonWebServiceResponse
        /// <summary>
        /// Unmarshaller the response from the service to the response class.
        /// </summary>  
        /// <param name="context"></param>
        /// <returns></returns>
        public override AmazonWebServiceResponse Unmarshall(JsonUnmarshallerContext context)
        {
            InvokeResponse response = new InvokeResponse();

            var ms = new MemoryStream();
            Amazon.Util.AWSSDKUtils.CopyStream(context.Stream, ms);
            ms.Seek(0, SeekOrigin.Begin);
            response.Payload = ms;
            if (context.ResponseData.IsHeaderPresent("X-Amz-Function-Error"))
                response.FunctionError = context.ResponseData.GetHeaderValue("X-Amz-Function-Error");
            if (context.ResponseData.IsHeaderPresent("X-Amz-Log-Result"))
                response.LogResult = context.ResponseData.GetHeaderValue("X-Amz-Log-Result");
            response.StatusCode = (int)context.ResponseData.StatusCode;

            return response;
        }