Caliburn.Micro 绑定子ViewModel绑定父Vi

<ScrollBar Margin="4"
                      Maximum="500"
                      Minimum="0"
                      Orientation="Horizontal"
                      SmallChange="1"
                      Value="{Binding Pa.TimeOffset}"

private GridSplitterResizeViewModel _pa;

        public GridSplitterResizeViewModel Pa
        {
            get => _pa;
            set
            {
                _pa = value;
                NotifyOfPropertyChange(()=>Pa);
            }
        }