code: @Override protected AutoBuffer writeAll_impl(AutoBuffer ab) {
      //Metalearner
      ab.putKey(_output._metalearner._key);
      //Base Models
      for (Key<Model> ks : _parms._base_models)
          ab.putKey(ks);
      return super.writeAll_impl(ab);
    }
docs: Write out models (base + metalearner)