Is there a way to have multiple options set as the default within a!facet function?

I have a requirement to set the defaultoption for a!facet to multiple values (same as if the user did a multi select in the UI themselves) and cannot get this to work.

I am able to set a default as a single value without any problems, but the system seems to ignore an array as the defualtoption.

Any ideas how I can achieve this? thanks