What is @SkipSelf decorator in Angular?

The @SkipSelf decorator tells DI to look for a dependency in the whole tree starting from the parent injector

I came across the @SkipSelf decorator as below. What does this @SkipSelfdecorator exactly mean in this case?

class Dependency {}
@Injectable()
class NeedsDependency {
  constructor(@SkipSelf() public dependency: Dependency) { this.dependency