UFile (package = ) [public final class AssertionKt {...]
    UClass (name = AssertionKt) [public final class AssertionKt {...}]
        UMethod (name = foo) [public static final fun foo() : java.lang.String {...}]
            UBlockExpression [{...}] : PsiType:Void
                [!] UnknownKotlinExpression (PROPERTY) [[!] UnknownKotlinExpression (PROPERTY)]
                UReturnExpression [return [!] UnknownKotlinExpression (POSTFIX_EXPRESSION)] : PsiType:Void
                    [!] UnknownKotlinExpression (POSTFIX_EXPRESSION) [[!] UnknownKotlinExpression (POSTFIX_EXPRESSION)]
