tooltipTextStyle property Null safety

TextStyle? tooltipTextStyle

Specifies the appearance for the tooltip in the SfSlider, SfRangeSlider, and SfRangeSelector.

This snippet shows how to set tooltip label style in SfRangeSliderThemeData.

SfRangeValues _values = SfRangeValues(4.0, 8.0);

    body: Center(
        child: SfRangeSliderTheme(
            data: SfRangeSliderThemeData(
                tooltipTextStyle: TextStyle(color:,
                fontSize: 16, fontStyle: FontStyle.italic),
            child:  SfRangeSlider(
                min: 2.0,
                max: 10.0,
                values: _values,
                interval: 1,
                showTicks: true,
                showLabels: true,
                showTooltip: true,
                onChanged: (SfRangeValues newValues){
                    setState(() {
                        _values = newValues;


final TextStyle? tooltipTextStyle;