GaugeAnnotation constructor
      const
      GaugeAnnotation({ 
    
- Key? key,
- double? axisValue,
- GaugeAlignment horizontalAlignment = GaugeAlignment.center,
- double? angle,
- GaugeAlignment verticalAlignment = GaugeAlignment.center,
- double positionFactor = 0,
- required Widget widget,
Create an GaugeAnnotation with the required properties.
The arguments positionFactor must not be null and positionFactor must
be non-negative.
Implementation
const GaugeAnnotation({
  Key? key,
  this.axisValue,
  this.horizontalAlignment = GaugeAlignment.center,
  this.angle,
  this.verticalAlignment = GaugeAlignment.center,
  this.positionFactor = 0,
  required this.widget,
}) : assert(
       positionFactor >= 0,
       'Position factor must be greater than zero.',
     ),
     super(key: key, child: widget);