How to filter based on property of an association?

Can anyone help please with this. I want to filter by properties of an association (expand) when reading from an external service. Not sure how it is done. This is is the property of the column that I need to filter on. req.query.SELECT.columns = [

“firstName”,

“lastName”,

“empInfo/isContingentWorker”

]

want to filter by empInfo/isContingentWorker