@Override
      public KnownSizeRecordWriter writerFor(@NotNull K key) throws IOException {
        UnsyncByteArrayOutputStream stream = new UnsyncByteArrayOutputStream(64);
        try (DataOutputStream os = new DataOutputStream(stream)) {
          oldSchoolDescriptor.save(os, key);
        }

        return new ByteArrayWriter(stream.toByteArray());
      }
@Override
      public KnownSizeRecordWriter writerFor(@NotNull K key)