docs: public static <K, V> ConvertingComparator<Map.Entry<K, V>, K> mapEntryKeys(
  			Comparator<K> comparator) {
  		return new ConvertingComparator<Map.Entry<K,V>, K>(comparator, new Converter<Map.Entry<K, V>, K>() {
  
  			public K convert(Map.Entry<K, V> source) {
  				return source.getKey();
  			}
  		});
  	}