sourcecode for the balloonplot function from the gplots package

Hi,
I want to take a look at the sourcecode for balloonplot. I would appreciate it if I could get help on overcoming the following problem :

methods(balloonplot)

[1] balloonplot.default* balloonplot.table* ?

? ?Non-visible functions are asterisked

balloonplot.default

Error: object 'balloonplot.default' not found

How do I access the non-visible functions?
Thanks,
Ravi??