public int size() {
      return in.size();
    }
Container for a batch of tiles to be processed together in the encoder and writer threads.
<p>
The cost of encoding a tile may vary dramatically by its size (depending on the profile) so batches are sized
dynamically to put as little as 1 large tile, or as many as 10,000 small tiles in a batch to keep encoding threads
busy.

@param in  the tile data to encode
@param out the future that encoder thread completes to hand finished tile off to writer thread
planetiler-core/src/main/java/com/onthegomap/planetiler/archive/TileArchiveWriter.java