Get the type of extension that will be returned by the static API.
Defaults to the subclass instance type, but can be overridden by declare readonly __type__: OtherType in a subclass, so long as the
__new__() method is also overridden to return that
type.
Get the type of extension that will be returned by the static API.
Defaults to the subclass instance type, but can be overridden by
declare readonly __type__: OtherTypein a subclass, so long as the__new__()method is also overridden to return that type.