I have a bunch of csv files from which I need to extract the "user" and "hwid" columns from. The csv filter will pull out all of the columns and put them in a field called "data". I then use the prune filter to keep only these 2 fields. The prune filter will work just fine if the target is not defined, however once it is defined it refuses to work. I have looked through the documentation page and there doesnt seem to be a "target field" parameter for the prune filter. How can I prune only the fields inside of the "data" field?