chartDescription problem

i want to add chartDescription above xAxis and yAxis for units ,but i only found xAxis chartDescription,so i subclass BarLineChartViewBase and add another chartDescription above yAxis for units, i did it . but when i add it to my cocoapod it turn to a error " Method does not override any method from its superclass" in “internal override func initialize()”
i use charts 3.0.0, and how to do it or please add the new feature for me. the feature for me it's usefull！

Start with BarLineChartViewBase and the internal override func initialize() mentioned in the issue, checking how Charts 3.0.0 exposes chart descriptions and how the CocoaPod build differs from the subclass context. Confirm the intended placement for a second description above the yAxis and verify that the feature builds and displays correctly in the affected chart views.

Written by the indexing model from the issue text.