@Px abstract fun itemSize(drawable: Drawable, orientation: Int, groupCount: Int, groupIndex: Int): Int
Defines a custom size for each group of divider.
drawable - current divider's Drawable.
orientation - RecyclerView.VERTICAL or RecyclerView.HORIZONTAL.
groupCount - number of groups in a list (equal to the list size when the span count is 1).
groupIndex - position of the group (equal to the item position when the span count is 1).
Return
height for an horizontal divider, width for a vertical divider (expressed in pixels).