exception when calling chart.tooltip.show()

Hello,

I have a c3 pie chart and I'm trying to manually invoke the tool tip when I hover over the legend.

I looked at the example from this thread here: https://github.com/c3js/c3/issues/509

but this doesn't seem to be working for me.

When I say: chart.tooltip.show({x:1}); it tells me:


I think I know the bounding client rectangle it's talking about but I don't know how to get it or pass it into the show() function.

Please help. Thank you.