code: public final LocalCompressedForest fetch() {
      int ntrees = _treeKeys.length;
      CompressedTree[][] trees = new CompressedTree[ntrees][];
      for (int t = 0; t < ntrees; t++) {
        Key[] treek = _treeKeys[t];
        trees[t] = new CompressedTree[treek.length];
        for (int i = 0; i < treek.length; i++)
          if (treek[i] != null)
            trees[t][i] = DKV.get(treek[i]).get();
      }
      return new LocalCompressedForest(trees, _domains);
    }
docs: Fetches trees from DKV and converts to a node-local structure.
  @return fetched trees