Gtk.TreeDragSource::drag_data_delete

function vfunc_drag_data_delete(path:Gtk.TreePath):Boolean {
}

Asks the Gtk.TreeDragSource to delete the row at path, because it was moved somewhere else via drag-and-drop. Returns false if the deletion fails because path no longer exists, or for some model-specific reason. Should robustly handle a path no longer found in the model!