Excluding whole rows from being staged based on certain criteria - mapper?

Summary:

In OIC Gen 3

I have the response from an API call being mapped directly to a stage file write.

So ALL the rows returned are immediately written.

I want to exclude certain rows based on criteria, e.g

"Only include rows where

Col A = 'A' and Col B IN (1,2,3)

or

Col A = 'B' and Col B IN (4,5,6)

etc

I assume I have to remove the map from the API response to the Stage.

Put in a For Loop

Go through each row one by one, use a Switch to check the conditions and only stage each row if it meets the criteria.