Callback function name backward incompatibility

[Jerry]

I notice that when you delcare a callback, e.g.,

viz.callback(viz.KEYDOWN_EVENT, myKey)

you can no longer put the function name in single quotes, e.g.,

viz.callback(viz.KEYDOWN_EVENT, 'myKey').

Is it possible to make both versions work in Viz3. Otherwise I will have
to change it in all the scripts I've written in Viz2.