"A comparator for [[Entry]]s which compares their items 
 according to the given [[comparing]] function.
 
     value sortedEntries = map.sort(byItem(byIncreasing(String.lowercased)));
 
 This function is intended for use with [[Iterable.sort]]
 and [[Iterable.max]]."
see (`function byKey`)
shared Comparison byItem<Item>(Comparison comparing(Item x, Item y))
            (Object->Item x, Object->Item y) 
        given Item satisfies Object => 
                comparing(x.item, y.item);