UFile (package = ) [public abstract interface Foo {...]
    UClass (name = Foo) [public abstract interface Foo {...}]
        UMethod (name = bar) [public default fun bar() : java.lang.String {...}]
            UBlockExpression [{...}] = Nothing
                UReturnExpression [return "Hello!"] = Nothing
                    ULiteralExpression (value = "Hello!") ["Hello!"] = "Hello!"
    UClass (name = Baz) [public final class Baz : Foo {...}]
        UMethod (name = Baz) [public fun Baz() = UastEmptyExpression]
