enum for Corona Renderer

I'm writing a script which involves using a post render callback that opens vfb+.

Thing is if I fire up the interactive rendering it pops up using corona renderer.

The developer answered:
hi, can you try querying vfb_type property? Values are:

enum VfbType {
    VFB_NONE   = 0,
    VFB_NATIVE = 1,
    VFB_WX     = 2,
    VFB_DOCKED = 3,

How is it possible to write this in a mxs fn to check against these?

CORONA TOPIC FOUND HERE: https://corona-renderer.com/forum/index.php/topic,12943.0.html