c_gtk_tree_view_set_drag_dest_row

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
__gshared extern (C)
void function(GtkTreeView* treeView, GtkTreePath* path, GtkTreeViewDropPosition pos) c_gtk_tree_view_set_drag_dest_row;

Meta