PieData constructor
PieData({})
Creates a pie chart segment.
label must not be empty. value must be a number (int, double) or a numeric string.
color is required for rendering.
showValue defaults to true to display the value on the chart.
Throws an AssertionError if value is negative or not finite,
or if label is empty.
Implementation
PieData({
required this.label,
dynamic value = 0.0,
required this.color,
this.showValue = true,
this.showLabel = true,
this.circleSize = 18.0,
}) : value = _parseValue(value);