def exec_download(download_path, op, params)
      exec_api_download(JsonRequest.new(op, params), download_path)
    end
def exec_download(download_path, op, params)
      exec_api_download(JsonRequest.new(op, params), download_path)
    end
Execute the given API download request

 @param [String] download_path     Absolute filename to download requested file to
 @param [String] operation  Name of operation
 @param [Array] params  Array of parameters; must ve valid JSON types

 @return [JsonResponse]