Stop Parent playing

I have a reference to a symbol nested in another symbol

var myvar = sym.getSymbol('symA').$('symB');

This stops playing of symB:

myvar.stop();

How can I stop playing of symA? I have tried this:

myvar.getParentSymbol().stop();

But it doesn't work.

(The nested symbol is dynamically passed into a function so I can't just reference it directly).

Thanks!!