angularjs - How to get the model of the target list model in ui.sortable? -

i've been pouring on documentation , cant figure 1 out.

when drag element on position in list can use ui.item.sortable.model in on callback model of item dragging. there no way me list im dropping , therefore no way validate whether item type in dragging valid item im dragging into.

how can target list dragging over? bear in mind need able target list before item dropped, otherwise not able show user action trying make invalid.