A shape with a notch in its outline.
Typically used as the outline of a 'host' widget to make a notch that
accommodates a 'guest' widget. e.g the BottomAppBar may have a notch to
accommodate the FloatingActionButton.
Abstract const constructor. This constructor enables subclasses to provide
const constructors so that they can be used in const expressions.
The hash code for this object.
A representation of the runtime type of the object.