@Override
    public void close() {
      keyToValuesIndex.release();
      try {
        values.close();
      } catch (IOException e) {
        throw new UncheckedIOException(e);
      }
    }
A map from {@code long} to {@code long} where each putAll replaces previous values and results are returned in the
same order they were inserted.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/LongLongMultimap.java