What is template-data used for in the form viewer?

[mindscratch]

In the demo code, the form viewer has its template-data property set equal to a json object, but I'm unclear about its purpose.

The documentation for the form viewer doesn't describe this property either.

[mwasiluk]

It can be used for template data interpolation in questions.
You can see it used eg. in http://wasiluk.io/angular-surveys/material/ question:

Is {{person.name}} age {{person.age}}?

which gets interpolated in viewer to:

Is Bob age 33?