Tooltip in Bullet Chart (CCCv2)

I would like to display certain values for my bullet chart tooltip. I notice, however that you cannot use the same kind of methods to get the values. For example, the following doesn't work (and probably b/c it doesn't make sense in the case of a bullet chart):

function(scene){
return scene.vars.category.value;
}

How can I extract the values from the tooltip that hold the title, subtitle, mark1, mark2, and maximum in a function under tooltipFormat setting for the BulletChart type in CCCv2?

Thank you!