His code above is already using a stream 
. The output of:
|> File.stream!()
|> NimbleCSV.RFC41080.parse_stream()
is a stream. What his code doesn’t need is Enum.map. It could just be Enum.each, provided nobody is using the result of column_data.
That’s why I’d like to see how column_data is called. @kylelw23 can you show us?
