collection = createCollection(key);
    }
    return wrapCollection(key, collection);
  }

  /**
   * Generates a decorated collection that remains consistent with the values in the multimap for
   * the provided key. Changes to the multimap may alter the returned collection, and vice versa.
   */
  Collection<V> wrapCollection(@ParametricNullness K key, Collection<V> collection) {

        return Collections.unmodifiableList((List<E>) collection);
      } else {
        return Collections.unmodifiableCollection(collection);
      }
    }

    @Override
    Collection<V> wrapCollection(@ParametricNullness K key, Collection<V> collection) {
      if (collection instanceof List) {
        return wrapList(key, (List<V>) collection, null);
      } else if (collection instanceof NavigableSet) {

        return Collections.unmodifiableList((List<E>) collection);
      } else {
        return Collections.unmodifiableCollection(collection);
      }
    }

    @Override
    Collection<V> wrapCollection(@ParametricNullness K key, Collection<V> collection) {
      if (collection instanceof List) {
        return wrapList(key, (List<V>) collection, null);
      } else if (collection instanceof NavigableSet) {