build method 
    
    
    
  Implementation
  @override
Widget build(Context context) {
  var current = child;
  if (child == null && (constraints == null || !constraints!.isTight)) {
    current = LimitedBox(
        maxWidth: 0,
        maxHeight: 0,
        child: ConstrainedBox(constraints: const BoxConstraints.expand()));
  }
  if (alignment != null) {
    current = Align(alignment: alignment!, child: current);
  }
  if (padding != null) {
    current = Padding(padding: padding!, child: current);
  }
  if (decoration != null) {
    current = DecoratedBox(decoration: decoration!, child: current);
  }
  if (foregroundDecoration != null) {
    current = DecoratedBox(
        decoration: foregroundDecoration!,
        position: DecorationPosition.foreground,
        child: current);
  }
  if (constraints != null) {
    current = ConstrainedBox(constraints: constraints!, child: current);
  }
  if (margin != null) {
    current = Padding(padding: margin!, child: current);
  }
  if (transform != null) {
    current = Transform(transform: transform!, child: current);
  }
  return current!;
}