TooltipDataTemplate in rollovermodifier in javascript

Hello, i want to customize tooltip in graph (SplineBandRenderableSeries), i can change the tooltip content but if i return svg like your example ( return <svg width="${width}" height="${height}">
<circle cx="50%" cy="50%" r="50%" fill="${tooltipColor}"/>
<svg width="100%">
<text y="40" font-size="13" font-family="Verdana" dy="0" fill="${tooltipTextColor}">
<tspan x="15" dy="1.2em">${tooltipTitle}</tspan>
<tspan x="15" dy="1.2em">x: ${seriesInfo.formattedXValue} y: ${seriesInfo.formattedYValue}</tspan>
</text>
</svg>
</svg>))
It doesn’t work. I have this error in console: Error from chart in div band0 TypeError: valuesWithLabels.reduce is not a function
and
Error from chart in div band0 DOMException: Failed to execute ‘removeChild’ on ‘Node’: The node to be removed is not a child of this node.
at RolloverTooltipSvgAnnotation.delete …

My graph has 3 renderableSeries (1 XyDataSeries and 2 XyyDataSeries)

Please can you send me an example in (javascript) for modify tooltip styling ?

Thanks.