BorderRadiusDirectional.vertical constructor

const BorderRadiusDirectional.vertical({Radius top: Radius.zero, Radius bottom: Radius.zero })

Creates a vertically symmetric border radius where the top and bottom sides of the rectangle have the same radii.

Implementation 

const BorderRadiusDirectional.vertical({
  Radius top = Radius.zero,
  Radius bottom = Radius.zero,
}) : this.only(
  topStart: top,
  topEnd: top,
  bottomStart: bottom,
  bottomEnd: bottom,
);