checkNotNull(keyPredicate);
    Predicate<Entry<K, ?>> entryPredicate = keyPredicateOnEntries(keyPredicate);
    return (unfiltered instanceof AbstractFilteredMap)
        ? filterFiltered((AbstractFilteredMap<K, V>) unfiltered, entryPredicate)
        : new FilteredKeyMap<K, V>(checkNotNull(unfiltered), keyPredicate, entryPredicate);
  }

  /**