package incr_dom_partial_render

move_focus gives the next element starting from the given key in the given direction according to the order of elements in the map. If the given key is None, move_focus returns the first element in the map for direction Next, and the last element in the map for direction Prev. If the given key is already the last element in the table for direction Next, or the first element in the table for direction Prev, then move_focus returns None.