code: @Nullable public <VS> VS getViewState(@NonNull String viewId) {
      PresenterHolder holder = presenterMap.get(viewId);
      return holder == null ? null : (VS) holder.viewState;
    }
docs: Get the ViewState for a given {@link MvpView} if exists or <code>null</code>
  
  @param viewId The mosby internal view id
  @param <VS> The type tof the {@link MvpPresenter}
  @return The ViewState for the given view id or <code>null</code>