PropsBuilder class Null safety

All class which hold the properties of the widget needs to extends this so that they can override the toJson and have their own implementation of the class for Eg

class BorderProps implements PropsBuilder {
  final String? borderWidth;
  final String? borderLeft;
  final String? borderRight;
  final String? borderTop;
  final String? borderBottom;
  final String? borderStyle;
  final String? borderColor;
  final String? borderRadius;
  final String? borderBottomLeftRadius;
  final String? borderBottomRightRadius;
  final String? borderTopLeftRadius;
  final String? borderTopRightRadius;
  final String? borderLeftRadius;
  final String? borderRightRadius;
  final String? borderTopRadius;
  final String? borderBottomRadius;