code: func (db *DB) LastPullSubscriptionChunk(bin uint8) (c *ChunkDescriptor, err error) {
  	item, err := db.pullIndex.Last([]byte{bin})
  	if err != nil {
  		if err == leveldb.ErrNotFound {
  			return nil, chunk.ErrChunkNotFound
  		}
  		return nil, err
  	}
  	return &ChunkDescriptor{
  		Address:        item.Address,
  		StoreTimestamp: item.StoreTimestamp,
  	}, nil
  }
docs: // LastPullSubscriptionChunk returns ChunkDescriptor of the latest Chunk
  // in pull syncing index for a provided bin. If there are no chunks in
  // that bin, chunk.ErrChunkNotFound is returned.