So I have secondary Y-axis enabled (i.e. pygal.add('SomeLabel', data_point, secondary=True)) and some of the tooltips for certain data points are showing up as None when you hover over them.

I have Nones in my data points, and by default pygal is supposed to ignore the None data points. While it is doing that correctly when it renders the line, it does seem to screw up the tooltips when secondary=True is set. This doesn't happen when I add data points with the default Y-axis setting. Do you know what is going wrong here?

I had mistakenly submitted this issue to s3rvac's fantastic pygal-toggle-graphs repository. His sharp eye pointed out that the bug actually resides within pygal, so I am resubmitting the issue here.