merge method
Implementation
ZeroTooltipStyle merge(ZeroTooltipStyle? other) {
if (other == null) return this;
return copyWith(
backgroundColor: other.backgroundColor,
lightBackgroundColor: other.lightBackgroundColor,
darkBackgroundColor: other.darkBackgroundColor,
textStyle: textStyle?.merge(other.textStyle) ?? other.textStyle,
borderColor: other.borderColor,
duration: other.duration,
);
}