Custom visual report page tooltip

I have created a simple custom visual for use as a footer which just displays when data has been updated .
like
"Data refresh: 12/12/2024"
and a Coloured circle with Red Amber Green to show how long ago it was updated.
It works fine.

I want to add a Tooltip which will just be a report page tooltip.
i have it showing in the formatting option. 

But I am struggling to understand how to get the add tooltip function to work as it doesn't use data points or D3 library
I have been following 
https://learn.microsoft.com/en-us/power-bi/developer/visuals/utils-tooltip#itooltipservicewrapperaddtooltip
I am not sure how I can define these values in addTooltip

this.tooltipServiceWrapper.addTooltip(barSelectionMerged,
        (dataPoint: BarChartDataPoint) => this.getTooltipData(dataPoint),
        (dataPoint: BarChartDataPoint) => dataPoint.selectionId
        );