UFile (package = ) [public abstract interface Foo {...]
    UClass (name = Foo) [public abstract interface Foo {...}]
        UMethod (name = bar) [public fun bar() : java.lang.String {...}]
            UBlockExpression [{...}]
                UReturnExpression [return "Hello!"]
                    ULiteralExpression (value = "Hello!") ["Hello!"] : PsiType:String
    UClass (name = Baz) [public final class Baz : Foo {...}]
        UMethod (name = Baz) [public fun Baz() = UastEmptyExpression]
