Snapd REST API: unset config option

How can I call “snap unset” using REST API? I see GET/PUT requests for conf, but nothing like unset.
Calling option with a “None” value from python does not appear to achieve the same effect (rpi config does not get modified and I call snap unset the option is commented out).

just been trying to do this myself and it seems a value of the string “null” removes the config item

ah, that only works with snap set

there is further discussion here Managing snap configuration