@Override public void putAll(Map<? extends String, ? extends V> map) {
        Set entries = map.entrySet();
        for (Iterator<Entry<? extends String, ? extends V>> iterator = entries.iterator(); iterator.hasNext();) {
            Entry<? extends String, ? extends V> entry = iterator.next();
            put(entry.getKey(), entry.getValue());
        }
    }
Converts keys to lower case.
<p/>
Returns null if key is null.

@param key the key convert
@return the converted key
jphp-runtime/src/php/runtime/common/collections/map/CaseInsensitiveMap.java