valid_vid

declaration:

::Lua
    function valid_vid(vid) => true or false

Checks VID maps to a real object or not.

** caveats: **

With a properly coded script, this shouldn't be needed at all. It is provided to assist debugging. It may give false positives in scripts with a high create/delete cycle (VIDs may wrap around and a dangling reference actually become valid again but for the wrong object).