How I can build file name of "S3 File Writer" consumed from data stream?

From the very first, I have data stream like as below

[{
"report_pipeline_id":"5fac56734418fe353b7b846d",
"transaction_id":"72479d9c-85f4-4cc6-90ec-dffac6d8536a",
"client_id":"e2572c18-29de-46c1-a212-fa54f61e468f"
},...]

later step is CSV Formatter, this step returns 

[{
"content-type":
"text/csv; charset=utf-8"
}]

Last step is "S3 File Writer". How can I set File Name of "S3 File Writer" = $report_pipeline_id + $transaction_id - it's get from the first step? Thank you!