Update CSV with existing HFS table or FC

[TL2]

I am trying to update a CSV hosted in AGO with a table or feature layer.  

I am able to export the HFS item as a csv hosted in AGO but when I try to use the code below it does not update the CSV.   Any advice?

csv = portal_item.export(title="test",export_format="CSV",parameters={"layers":[{"id":9}]})
item = gis.content.get("a5b6f0756f474aaca8f9f159ebd08c1e")
item.update({}, csv)