public Collection<V> values() {
        return new ValuesView<K, V>(this);
    }
Gets the previous key to the one specified using insert order.
This method performs a list search to find the key and is O(n).

@param key the key to find previous for
@return the previous key, null if no match or at start
jphp-runtime/src/php/runtime/common/collections/map/ListOrderedMap.java