example when override keyword is useful

```scala
trait T {
  def soAbstract(x: X, y: Y)
}

abstract class C extends T {
  //I think that I implement soAbsract
  def soAbstract(y: Y, x: X) {
    //but I do not
  }
}
```

The problem will occur only when non abstract class/object of C will be implemented.