}

    Map<K, ImmutableCollection.Builder<V>> ensureBuilderMapNonNull() {
      Map<K, ImmutableCollection.Builder<V>> result = builderMap;
      if (result == null) {
        result = Platform.preservesInsertionOrderOnPutsMap();
        builderMap = result;
      }
      return result;
    }

    ImmutableCollection.Builder<V> newValueCollectionBuilderWithExpectedSize(int expectedSize) {