code: private void cleanGlobalBlockList() {
      for (Iterator<Block> globalBlockListIterator=globalBlockList.keySet().iterator();
      globalBlockListIterator.hasNext();) {
        Block block = globalBlockListIterator.next();
        if(!movedBlocks.contains(block)) {
          globalBlockListIterator.remove();
        }
      }
    }
docs: /* Remove all blocks from the global block list except for the ones in the
  moved list.