Cancellable
constructor()
Creates a new #GCancellable object.
Applications that want to start one or more operations that should be cancellable should create a #GCancellable and pass it to the operations.
One #GCancellable can be used in multiple consecutive operations or in multiple concurrent operations.
Return
a #GCancellable.
constructor(pointer: <Error class: unknown class><<Error class: unknown class>>)