@pavelgj I will not add '@override` as part of this PR because:
1. This should be done globally if we decide to do so,
2. We should discuss & agree before doing doing

Also there is this comment on `override` in the core:

```
 * Use the `@override` annotation judiciously and only for methods where
 * the superclass is not under the programmer's control, the superclass is in a
 * different library or package, and it is not considered stable.
 * In any case, the use of `@override` is optional.
 *
 * For example, the annotation is intentionally not used in the Dart platform
 * libraries, since they only depend on themselves.
```